Model S Fire | Hacker News Reader

Model S Fire

teslamotors.com

594 pointsshakes238 comments

I agree this isn't as big of a deal as the stockmarket may imply, but this line bothers me:

"That equates to 1 vehicle fire for every 20 million miles driven, compared to 1 fire in over 100 million miles for Tesla. This means you are 5 times more likely to experience a fire in a conventional gasoline car than a Tesla!"

Americans drive an aggregate of 3 trillion miles every year, while Tesla drivers have done 100 million (and they don't cite this number; are they including test drives?). That's well over an order of magnitude difference. Plus, the average Tesla driver is currently probably a superior driver (if for no other reason than they have a brand new expensive car) and has taken better care of their car (since it's within 2-3 years old, tops). In theory, Teslas will eventually become more mainstream over the years -- resold, price drops, lower-end models, etc.

Again, I don't think their conclusion about Teslas being safer overall is wrong. However, their conclusion of the likelihood of a Tesla catching on fire seems off, and the exclamation mark makes this press release seem glib.

> Americans drive an aggregate of 3 trillion miles, while Tesla drivers have done 100 million. That's well over an order of magnitude difference.

The data on 100 million is probably enough to compare with the 3 trillion miles. The populations don't need to be equal to compare them, just big enough that they are random and distributed enough.

To put it in perspective, the disparity is equivalent to polling 10K americans and extrapolating to all of america (which, for better or for worse, is what most pollsters do).

If the sample is truly random, it doesn't matter what the population size is. Of course, truly random samples are hard to get.

That depends on the population variance.

Except pollsters put in a lot of effort in making sure that the sample is representative of the larger population.

Which is not true here, as the GP correctly notes.

Do they really? My only interaction with pollsters has been either having them call me or solicit me on the street, and both approaches have a tremendous inherent bias. As far as I know, this is how the big national agencies do things.

There are all kinds of adjustments done afterwards to correct for various factors. For example, you know the age distributions in USA; and if you find out your phone calls are getting twice as many seniors than the proportion should be[1], then you throw away a random parts of them so that they don't skew final 'data' towards the typical opinions of seniors.

[1] Assuming that you're not measuring average age or measuring 'who is at home', but if you want to see, say, the average political opinion of total USA population, which tends to correlate with age.

It still seems impossible to correct for everything. Sure, you could correct for age as you describe, but I imagine that landline phone ownership correlates with political opinions in all sorts of other ways too.

Furthermore, how do you gather the data needed to correct the polling numbers without being able to accurately poll people in the first place? Seems like a complete chicken-and-egg problem.

"how do you gather the data needed to correct the polling numbers" -> you use the census. You need some info about the total population, you get it periodically and it doesn't change that much; you don't need to repeat it for every survey.

The census doesn't tell you about most of the godzillion factors that link landline phone ownership with political opinions.

I often see polls of 1K Americans and extrapolating out from there. An example: http://www.webpronews.com/americans-think-cloud-computing-co...

Of course, the refrain I often hear is that as long as you pick the RIGHT 1,000 Americans, it's as good as polling all 319 million.

> Of course, the refrain I often hear is that as long as you pick the RIGHT 1,000 Americans, it's as good as polling all 319 million.

If it's a proper random sample, then it's far better than sampling all 319 million because it's 95% accurate with about a 3% margin of error and vastly cheaper and actually practical; you can't poll 319 million people.

It's counterintuitive, but the sample size needed for a good measurement doesn't much depend on the size of the overall population. What matters is getting a properly random sample. This is where pollsters fall down, because their "random" sample tends to be heavily biased toward the sort of person who has a landline telephone and doesn't hang up on pollsters.

Polling 10,000 Americans would be vast overkill, in any case.

You say that as if 10k is too small a sample size to extrapolate accurately with, but actually that's a huge sample size that if done properly would be extremely accurate. You don't need to poll anywhere near 10k people to accurately predict all Americans views.

You can sample less than 2000 people and get 99% accuracy with a 3% margin of error for a population of 325 million. Increasing the sample size to 10k simply reduces the margin of error to 1.29%, hardly worth the extra sampling of 8k people.

If you haven't read Asimov's Election Day, I highly recommend it.

When trying to get popular opinion for, say, an election -- sure.

However, there was one fire over 100 million miles. The problem isn't the 100 million, it's the 1 fire. This wasn't a controlled experiment, either -- they just stopped the clock as soon as the first fire happened, and multiplied. A week ago, they could have said "You have exactly a 0% chance of your Tesla catching on fire" and have been right by this logic.

To think of it another way -- let's say you get lucky and get a hole-in-one your 10th time golfing. Does that mean you'll have 10 hole-in-ones if you golf 100 times? Doubtful.

EDIT: Also, don't forget that Elon is mixing numbers. There's no fire if someone doesn't run over something. All these numbers show is that the average driver is more likely to run over something. Of course Tesla drivers run over fewer things -- there are no 16 year old kids texting while driving a Tesla... yet.

Doesn't stopping the clock after 1 fire just penalize them, not benefit them?

That said, I also think the 1 fire is the problem here. Just think about how that relation changes with 2 fires.

It probably penalizes them, assuming the no-fires-for-100m-miles was not a fluke. There's no way to know for sure without knowing the true distribution of fires per mile.

The chance goes from 0.000000010 to 0.000000020

If I had the cash I would still purchase a Tesla after the second fire as well.

Thanks for converting that to "fires per mile".

More miles would have been driven, so less. I'd be happy after the hundredth fire. They'll be even safer by then.

You example just reinforces the point.

Please don't argue against statistics (mathematical information based on fact) when you don't understand them.

Did you consider the possibility that it is in fact you who don't understand?

The Law of Large Numbers states that as more miles are traveled, the fires per mile will approach the expected value. It is entirely possible to have 10 fires in the next week.

We won't know what the expected fires/mile is until a much larger sample is collected. It will take years to prove out.

Why do you believe a larger sample is needed? At what sample size would you believe that the Tesla averages less fires than other cars?

Here's a question (for anyone in this thread arguing statistics) that has an actual numerical answer: given the information in the article, what is the probability that Tesla's indeed experience less fires per mile than other cars? If someone doesn't know how to calculate the answer to that question, he shouldn't be arguing here.

Let's see if I remember any of this. If we assume the null hypothesis that Teslas have 1 fire per 20 million miles same as other cars, then P(0 fires in 100 million miles) = 0.67% and P(1 fire in 100 million miles) = 3.4% from Poisson distribution. So the odds that you'd have no more than 1 fire in 100 million miles is 4%. So I reject the null hypothesis with a p value of 0.04. (edit: fixed values)

This seems a bit dodgy since I'm "designing the experiment" after the fact, but I'm not sure how to correct for that. Any Bayesian experts?

Assume a Tesla vehicle has a constant risk of catching fire per mile. That is, we have a exponential distribution `P(catch fire after t miles | hazard rate) = P(t|a) = a exp(-at)` where `a` is the hazard rate (average fires per mile). Furthermore we'll assume an exponential prior on `a`: `P(a) = w exp(-wa)`. `w` is a parameter that expresses how much prior knowledge we have of `a`. In the limit `w=0` we know nothing at all, except that it's nonnegative.

Our data is the fact that we went 100 million miles before a fire, after which exactly one fire happened, so we want to find the distribution `P(a|t = 100 million)` which tell us everything we want to know about `a`.

Then use Bayes' theorem: `P(a|t) = P(t|a) P(a) / P(t) = aw exp(-a(t+w)) / P(t)`. The normalization factor `P(t)` involves an integral over `P(t|a) P(a) da` from 0 to ∞, which wolfram alpha tells me evaluates as w / (t+w)^2.

So our posterior probability is `P(a|t) = a (w+t)^2 exp(-a(t+w))`, but we can take the limit `w -> 0` at this point for a fully uninformative prior: `P(a|t) = a t^2 exp(-at)`.

So we can just set `t=100e6 miles`, and now calculate things like the expectation of the distribution: `E[a] = 2/t = 2e-8 per mile`. Or the probability that the hazard rate is less than other cars, which is the integral from 0 to 1/(20 million miles): `P(a < b) = 1 - exp(-bt) (bt + 1) = 0.96`.

Why do you believe a larger sample is needed?

You need an exhauseted state space. You cannot empirically infer a legitimate probabliliy, eg n/100m miles) with only a single failure observation, if there are 100 possible ways to fail. At best you have data on (1) of (N) ways to fail, but surely in the case of car accidents N=large.

A total of 2,650 cars were delivered to retail customers in North America during 2012, 4,900 during the first quarter of 2013, and 5,150 during the second quarter of 2013

Assuming 13000 cars on the road, each car would have logged 9k miles to get 110m road miles, as quoted by Tesla. But we know from past industry experience, that road fires are proportionate also with fleet age.

So, if anything we the probability of a road fire is likely to go up as more failure modes are discovered (including by chance), and as the vehicles cycle through a normal working life.

By your "hole in one" argument, Tesla is "doubtful" to keep up their pace of one fire per 100 million miles. In other words, their "true" fire rate is actually less than one per 100 million.

You don't know that and this is the whole point of the "hole in one" argument.

If you assume that fires are normally distributed, it's equally likely to be a larger or smaller length of time to the next one.

Presumably it will go up to some degree over time as the average age of tesla's fleet converges with the industry average, as older cars are more likely to experience malfunctions/breakdowns for obvious reasons.

The median car in the US is ~11.6 years old[1], while Tesla's oldest vehicles were released in 2008, and the vast majority of their fleet was sold in the last couple years.

Obviously, the massive differences between electric powered cars and internal combustions engines means that they may never reach parity, but unless Musk has figured out a way to beat entropy, its pretty safe to assume that older cars will break down/suffer leaks/explode more than newer ones.

[1]https://www.polk.com/company/news/polk_finds_average_age_of_...

I think a Poisson distribution is what you're looking for here. Roughly, if events happen independently and with a fixed probability per time interval, you get a Poisson distribution. Poisson distributions apply to a lot of things, so it's a very useful distribution to know about.

But since the number of cars is increasing, it's not a Poisson distribution; if the chance per car per time is constant, you'd expect the time to the next fire to be shorter.

Forgetting about all of the (completely legitimate) concerns with this comparison aside from statistics, we can get a general idea from simple statistics how convincing having the first crash at 100 million miles should be.

For the purpose of our simple modeling, suppose that there is a constant risk per mile of the car catching fire, making an exponential model reasonable. Under this model, observing the first fire at 100 million miles would give a 95% confidence bound on the rate of fires of about one fire every 33 million miles.

If we're comfortable with the stated rate of about one fire every 20 million miles for other cars, then this would give a 95% confidence upper bound on the Tesla's rate of fires at about 60% of a normal car's rate. This isn't the 20% that Elon's statement would imply, but it does suggest a difference (which could just be due to other problems with the comparison).

> let's say you get lucky and get a hole-in-one your 10th time golfing. Does that mean you'll have 10 hole-in-ones if you golf 100 times? Doubtful.

This wasn't after driving 100 miles. Aren't you off by 6 orders of magnitude?

This is related to something called the Doomsday Argument, and it was recently the topic of an xkcd what-if blog:

http://what-if.xkcd.com/65/

By all accounts it comes down to the old bayesian/frequentist battle lines.

If I get the math right (assuming a Poisson distribution) then a week ago, based on 0 fires, they could've said with 90% confidence "The chance of your Tesla catching on fire is less than 2.3 cases per 100 million miles". Not 0; but not very high as well.

The relevant metric here seems to be 'miles between fire events'. On this metric, we have exactly 1 data point for Tesla. I would hardly call that "probably enough".

Of course, I'm exaggerating in the other direction. What we really should be calculating is the odds that Teslas burst into flames less often than the average car, given that the average car does so every 20 million miles and the first such event in a Tesla was at the 100 million-mile mark. We're still failing to account for the fact that the average Tesla is newer and probably better-kept than the average car, but it would at least be a reasonable start.

I don't know enough statistics to perform this calculation, but I would like to see how it is done.

An easy starting point would be to get this kind of data on similarly aged cars - cars sold over the last 2-3 years, then see what stats you can get there. I'd guess that you'd find some models that have never caught fire and some that have done so a lot more than tesla's, but that's pure speculation on my part.

We have enough events, because in this case it is appropriate to model the actual random event as 'million miles driven' with a chance of fire happening or not happening. Gasoline cars have a mean of 0.05 fires per million miles, and given the current Tesla data, the mean is 0.01 fires per million miles. I'm not taking out a calculator, but it would come out to an extremely low (0.0001%) the 'true' fire chance is the 0.05 gas car rate or higher; the 95% confidence interval should be 0.01 +- 0.02 or tighter, so still twice better than gas cars.

For an exaggerated example, if Tesla had driven a billion miles and had 0 fires, you shouldn't say that there's not enough data - you definitely would have enough data to say that the chance of fire is below the gas-car rate of 5 fires per 100 million miles.

Why is million miles driven a better way to model it than billion miles driven, for example? If you happen to choose that, there clearly isn't anywhere near enough data.

I'm honestly curious how one models this type of thing statistically, and I am not convinced enough of its obviousness to just accept numbers that someone throws around.

Hard to argue against Elon's last sentence, though.

That should be the main point of his argument, instead of speculative statistics.

I agree, the exclamation mark was a terrible thing to include. Imagine if someone died, would they still put the exclamation mark there?

The page is as much about marketing (maybe more) as it is about safety or the incident. Especially, after the stock dropped, can you blame them?

That said, I'm not really sure why this is such big news. Accident happened due to debris on the road. No one was hurt. The car was severely damaged, but got the owner to safety.

AND THEN a small fire happened...

Then I read things like this: http://www.dailynews.com/general-news/20130928/5-killed-1-in...

Let's consider this for a second - Tesla Model S had a no-injury accident and made national news. 5 kids burned alive in a Sentra, and this barely stayed on local news for 3 days.

Tesla Model S is a phenomenal vehicle with an excellent, if short-ish, track record. It really annoys me that reporters go out of their way for sensationalist articles, when there are far worse tragedies to cover.

> The page is as much about marketing (maybe more) as it is about safety or the incident.

What does that mean? Taking a common definition of "marketing" to be "expressing the value of a product to potential customers," any article that is about safety or about a recent product incident is also marketing. It sounds like you're using "marketing" as an ill-defined term that basically just means "something bad about the way a company publishes information."

"Bad" is subjective, when I personally think Marketing, I mean putting a spin on things and presenting it in a more favorable light for the company.

This is not a dry facts page, but a public relations communication that is intended to sell you on the fact that Tesla Model S is a safe vehicle. Nothing wrong with that and nothing "bad" as you seemed to imply.

But all of the claimed facts are either true or false, right?

Take a look at this statement:

"The nationwide driving statistics make this very clear: there are 150,000 car fires per year according to the National Fire Protection Association, and Americans drive about 3 trillion miles per year according to the Department of Transportation. That equates to 1 vehicle fire for every 20 million miles driven, compared to 1 fire in over 100 million miles for Tesla. This means you are 5 times more likely to experience a fire in a conventional gasoline car than a Tesla!"

Facts stated: * 150,000 car fires per year according to the National Fire Protection Association. * Americans drive about 3 trillion miles per year according to the Department of Transportation. * 1 fire in over 100 million miles for Tesla.

Sales pitch at the end: "This means you are 5 times more likely to experience a fire in a conventional gasoline car than a Tesla!".

The reason I call this a sales pitch or a marketing messaging, is that while the facts technically support this, as pointed out earlier, it's based on a data set of 1 occurrence.

Personally, I buy Musk's argument and if I was in the market for a new car, figuring out how to pay for Tesla would actually be at the top of the list for me. This story only re-enforces my own personal opinion that these are great cars.

"1 occurence" is misleading, as the miles driven is the actual random event. If you throw a coin 100 million times and 1 time it lands on its side - then you can have a rather reasonable estimate on how rare that possibility is even though you have just 1 occurrence. I.e., it may be that the chance is 0.5 per 100m or 2 per 100m; but it'd be very strange if the actual chance is 10 per 100m.

The reason it is such a big deal is of course that we're standing before a major disruption of the whole industry everybody is curious whether or not this new tech is viable or not.

I agree...The kind of driver who can buy a Tesla is likely the kind of driver who has acquired enough education and comfortable wealth to be a competent driver (on the average). Moreover, there's survivor bias here: If you've made it far enough in life to buy a Tesla, you're probably a person with pretty decent habits.

And finally, if you've bought an expensive car like the Tesla, you may be more likely to drive it more carefully than the average person does their Honda Accord.

I don't think Musk is any more dishonest than any other CEO, and he's probably more honest, by far, on average. However, it kind of pains me to see how easy it is for him to sway the hacker crowd with data-interpretations that would be questionable by any standard. If this is among the strongest empirical evidence he can provide, then I think we should maintain some skepticism.

A study by UC Berkeley and the University of Toronto actually showed that luxury car owners were by far the most aggressive drivers, and the least likely to stop for other road users.

http://www.bankrate.com/financing/cars/study-bmw-drivers-are...

For whatever reason BMW stood out most of all as the worst of the worst in this study, but 'expensive car drivers are better drivers' has been proven to not be an assertion you can make from common sense or intuition.

Without reading the study, I'm ready to agree that its conclusions are correct. But I'd argue we're still comparing apples to oranges here:

1. We can't assume that Tesla drivers are the same as traditional luxury car drivers. While cars are a statement of wealth, and many arrogant bastards like making that statement...A Tesla is ostensibly a statement of a few other things, such as concern for the environment, optimism about technology, etc. etc...in the same way, even though many programmers make high-end salaries (low-6 figures), I wouldn't say that we can expect these programmers to golf as much as the average non-programmer low-6-figure-earner.

2. Reading the link you posted, it said the study evaluated based on the frequency of accidents and the size of payout...I couldn't find the study on the website, but this statement from the article was ambiguous to me:

> According to data from IIHS website, the collision insurance losses on BMW 7 Series are more than twice the average for vehicles nationwide, and BMW 3 Series two-doors are more than three times.

Twice the average of what...? Payouts total? Payouts per claim? Payouts per claim normalized by number of total cars of that kind on the road?

3. The NHTS data concerns the number of fires. For the study you cited to be more relevant, we'd have to know what proportion of the insurance claims also involve vehicle fires. If you're thinking, "Well, if a car caught on fire, then that's likely because of an accident...so more accidents mean more fires"...well, a> That's a classic logical fallacy (All dogs are animals. Sara owns a lot of animals. Therefore, Sara owns a lot of dogs) and b> the kinds of accidents that make up a majority of insurance claims (my guess is low-to-medium speed fender benders) may not represent a significant portion of incidents that end up in a flaming wreck.

All in all, I wouldn't say that Musk is clearly wrong here...He could be right, we just don't have enough information either way...so it feels slightly dirty -- a slap in the face of analytical thinking -- for him to cite these statistics as being anywhere near conclusive.

> I agree this isn't as big of a deal as the stockmarket may imply

I firmly believe that what's happening on the stockmarket and the fire are merely a coincidence, there isn't a causal relation between them. Tesla stock has been due to correct back for a while, and a downgrade came in as well (unrelated to the fire).

Edit: first rule of the HN club: only positive things about Tesla, otherwise you are going to be voted down. Neutral opinion is considered negative. :)

> Plus, the average Tesla driver is currently probably a superior driver

I can play the conjecture game too.

The average Tesla driver is probably a worse driver than the average gas-powered car driver. Why? Because they have the disposable income to purchase a Tesla, which means they're probably less careful with their possessions (as they can presumably afford to replace them), plus the Model S is a sports car so they're probably driving faster and more carefree than your average person.

Not that I really believe this, but come on, your argument is completely made up.

I would counter with, "How dare you assume that all Tesla drivers have disposable income to throw around". I happen to be close to buying one and know a few other owners who are average middleish class people who normally would have bought a porsche or a tesla. I work in tech and as a result am paid pretty decent. Do I have disposable money (or my friends) to buy a Tesla Model S? No! However, given where I live and where I want to drive + the recharging stations, Tesla is a good option for me.

Do not assume just because someone is able to get enough money to buy something expensive,that they have tons of money. By that same logic, anyone who is able to buy a home is clearly flush with cash and able to throw it all around. Completely ridiculous.

You're missing the point - he's not actually making that argument, he's showing how easy it is to make any argument if you back it up with anecdotal conjecture rather than data.

Exactly. I rather suspect that Tesla drivers are actually comparable to other drivers, rather than being demonstrably better or worse, but the only way to know would be to actually conduct a study on the subject.

They will be demographically better if they're older, simply due to experience. If you look at insurance, the ridiculously expensive demographic is the male <25-year-old segment. If tesla drivers are underrepresented here - likely, since they're a luxury car at the moment - then yes, it's pretty safe to say that tesla drivers are more experienced, safer drivers.

Do not assume just because someone is able to get enough money to buy something expensive,that they have tons of money.

Or sense. Or street smarts. That was the OP's point.

Are you claiming that you have analyzed the Model S and found that due to money saved on gas it is financially cheaper than a conventional car over some timescale? If not, then I truly don't know what you're talking about.

I'm really confused by "average, middleish class people who normally would have bought a porsche or a tesla" - is that a typo? Did you mean "would not normally"? If not, your idea of "average middleish class people" is really oddly out of whack.

Many people by homes because of a calculation that owning a home is cheaper in the long run than paying rent over that same period of time. Many people buy homes not based on such a calculation and simply because they have disposable income and owning a home is nice. Many people also buy homes based on neither financial decision-making nor disposable income, and I seem to recall this having some negative impacts on our economy a few years back, which may make it a poor analogy to why it makes sense to buy a Tesla (or a porsche?!) without disposable income.

I work in technology and would be considered by some (not myself) a Linux expert. I am most certainly not upper class, but I am by no means lower class. I have several friends who also work in tech in similar roles for financial companies (like myself). One of them drives a BMV M5, one of them drives a used porsche 911 turbo. It isn't that a porsche or bmw is more or less expensive. It is something that they save up to buy for themselves. A normal car or a tesla both solve my needs, but a tesla is sure as hell a lot cooler for the sheer amount of tech and engineering. I don't really see where you think I claimed to see any money would be saved by a model S. I never alluded to anything of the sort. But I think this is OT and isn't really productive. Lets focus on tech here at HN and leave the flames for /., where they belong.

Not being among the richest people you know does not make you middle class.

Without looking, I'd like you to guess what the median personal income in the United States is, and then guess what the median household income is.

Then go look up the real numbers.

I suspect you're in for a surprise.

This is why politicians use "middle class" to describe who they're fighting for; it's a term that nearly everybody thinks of themselves as belonging to.

Roughly, middle class is <50k. You don't buy BMWs or Porsches when you do 50k$. Or at least, in most case it's not a wise idea to do so.

You're either being disingenuous or your perception of reality and normality is really skewed.

You certainly can buy a BMW or a Porsche if you make $50,000 a year, especially if you're single and living in a cheap part of the country. A used BMW 3-series will in many cases be less than a new Honda Odyssey minivan. But you'll be shopping on the used marketplace.

I'm not really sure what you being a Linux expert has to do with your opinion about the income of the middle class.

I laughed at that part too

You are far, far better off than you think you are.

You'll probably see the posts saying this to you as condescending, but if you can even think of purchasing a Model S you're in a very exclusive group of people.

You're pretty clearly upper middle class. The difference between upper middle and lower middle is the difference between a Tesla and a Hyundai.

Fun fact: 6% of American Express Centurion (Black) cardholder's own a Hyundai: http://www.autoevolution.com/news/hyundai-is-a-favorite-of-c...

If you make >100k, I can assure you, you are not middle class. You are part of the "not rich enough" class. This class has a lot of money and can reasonably do anything they want, but compare themselves to the ultra rich and think "I'm not rich". The problem is they are always looking up and forget to look down.

I grew up in a ~30k household in the 90's. Something I would call lower middle class. Upper middle class is probably ~70k-100k.

Please tell me you're taking into account cost of living here.

$100k does not go very far in San Francisco and Manhattan. Nobody making $100k in those places could reasonably afford a Tesla without severe over-spending (which they're welcome to do if they want to--whatever floats your boat). If you view the middle class as owning detached single family homes with yards, you would be lower middle class at best in those cities at $100k. If your spouse also made $100k, you could afford the crappiest single family home that was still livable.

But it's a really good salary in Denver or Houston; you could definitely find a nice house to buy and afford comfortably, though it might have a bit of a commute. If your spouse also made $100k, you could afford a nice home in any neighborhood with no commute.

And it might nearly qualify you as wealthy in a small rural town of 15k people total, where you would never need to spend more than $150k on any house.

Of course it's not a universal statement. Estimates are never aimed at outliers.

People in San Francisco, Manhattan, and London are a major constituency here... not outliers.

Population of earth: 7.1 billion.

Population of San Francisco: 0.8 Million.

Population of Manhattan: 1.6 Million.

Population of London: 8.1 million.

Percentage of the world's population living in either San Francisco, Manhattan or London: ~0.0015%

Exactly what do you think an outlier is? If you live in one of those three urban areas, you're already a member of an elite class.

He was referring to the Hacker News demographic, where these places are not such an outlier, and whether or not living in a place like San Francisco puts you in an elite class you still could not reasonably afford both a nice place to live and a Tesla there on $100k, which was my original point.

But I don't really understand why living in an expensive urban area automatically puts one in an elite class. The standard of living is not much better than other places for one thing--what you gain in diversity is lost in housing conditions. Also, it's not like $100k wages there are super rare. You don't need to be a 4.0 Ivy League graduate to score a livable wage in San Francisco. That's the starting salary for a lot of professions in cities like that, not just software developers. Police officers in the SFPD can make as much as a Twitter engineer fresh out of Stanford: http://www.sf-police.org/index.aspx?page=1655

Very good point. I would, however, write that as 0.15%.

Derp. Thanks.

Edit: I can't edit my prior comment. Time window?

Apparently.

I'm not crazy about percent notation. I find it confusing. I might have written it thusly:

> 0.0015 of Earth's population are living in San Francisco, Manhattan or London

Cost of living is always a factor. I live in the bay area. The salary of a programmer is usually 6 figures here. Granted it's almost impossible to buy a home but if you are frugal with your rent ( for instance getting roommates or living further from your job or in a less hip neighborhood) you have a pretty large amount of disposable income. Teslas don't cost less in South Dakota than northern California. I think cost if living is sometimes overstated because besides housing I don't find other critical staples like food, insurance, utilities to differ appreciably by state. If you want to own THEN the situation changes dramatically.

I'm not really sure what you're getting at. Having to move far out and getting several roommates just to swing the payments on your Model S is not exactly my idea of comfortably affording the car.

I wouldn't buy a Tesla on $100k in North Dakota either. Maybe, if I felt like blowing through money, I'd get a BMW 3 series or Audi A4, both of which are still considerably cheaper than a Model S.

I'm not disagreeing with you re: the Tesla S is way out of reach of someone "only" making $100k.

I was just pointing out that besides housing (especially owning) the cost of almost everything in CA is the same if you move somewhere where the cost of living is lower yet the salaries elsewhere are significantly less. So there is an opportunity to save a lot of money if you are willing to compromise somewhat on your living conditions.

I suppose it depends on whether you think it's important to own your home and/or you mind having roommates. When I first moved to CA I had severe sticker shock re: the rents so I rented a room in nice houses with other young professionals for the first 5 or so years I lived here.

Exactly. Also, California is the highest-taxed state in the republic, so adjust that pre-tax salary of $100K downward a bit more in real terms.

Consumer goods like cars and laptops and TVs will cost the same, to a first approximation, anywhere in the continental U.S. But in some coastal areas, you have real estate costs that are 20x that of cheaper areas with salaries/compensation packages that are generally not 20x higher. In central Pennsylvania towns the median household income, for instance, tends to be around $26K and the median house cost is $64K, meaning houses are 2.5X median income.

In Palo Alto, on the other hand, the median house cost is around $2.25M, and the median family income is around $160K, meaning houses are 13.75X median income. Part of this are older PA families who bought when land was cheap many decades ago and are grandfathered in with lower tax rates, but part of this is also people who are stretching their finances dangerously to be able to afford there. (Even though those $2.25M median homes are often smaller than the national average, measured by square footage.)

It's possible to make $100K in the SF bay area and be, in real terms, poorer than someone making half that in central Pennsylvania.

Here in SF, housing costs are significantly higher. Other costs are somewhat higher. But you know what isn't? Mass produced consumer goods for one. An xbox (or tesla) costs the same whether you make $100k in SF or $50k in middle America.

You know what else? Travel. Domestic and international travel is a LOT more affordable when you're making $100k in SF.

And a big one: Retirement. You sock away your SF salary for 40 years and then retire in a cheaper COL area with no state income tax.

The truth is, even here, $100k is a lot of money. It really is. It's not rich by any stretch, but it's certainly not average middle class living. It is frustrating that a couple making over $200k can hardly buy 1000sq ft house while staying inside 30% (of gross income) housing budget, a metric widely seen as "affordable housing." But still, on balance, that couple making $200k is doing very, very well.

And the truth is, there are a lot of engineers here that, with liquidity events (which might just mean vesting your RSU's in an already public company), are earning $200k a year. That literally puts you in the top 1% of wage earners. (But not in THE "1%" of course which is usually a term referring to net worth and not gross income. But still.)

Edit: The math is different of course if/when you add children to the mix. But I deliberately left them out, because in reality, it's just not a common lifestyle choice in San Francisco.

"You sock away your SF salary for 40 years and then retire in a cheaper COL area with no state income tax."

Small correction -- state income tax in CA is a big deal even if you're saving for retirement. And once you retire, you presumably won't care what the state income tax is.

That's not how it works.

Retirement savings goes into tax advantaged accounts like 401ks and iras. This is pre tax income. You pay the taxes at the end, when you're drawing from your accounts during retirement.

Not necessarily; you might have chosen a Roth for individual retirement savings. The contribution limit on that type of account is effectively higher than a traditional IRA, since it's expressed in post-tax dollars - very useful for someone trying to stash away as much as possible. Once the money is in the account, it grows tax-free.

But for those people, taxes are immediate rather than deferred.

Honestly, from the sound of it, you just googled retirement plans. :)

Actually, Roth IRAs are limited to $5000 a year per person, and once your income reaches ~$110k you can't deposit into a Roth at all. The vast majority of private retirement dollars are saved in 401k accounts that have have a cap much higher than in a Roth. Three times higher.

And actually, if you do the math (or just go read the math) you'll see that there is very little difference in your total retirement funds whether you use a pre-tax or post-tax account. This is because in a pre tax account you have the advantage of earning capital gains on the IRS's dime. The wisest choice is of course to use both if you can. Though many many people living in this area, due to income restrictions, cannot.

Anyway, I intended my reply to you as just honestly informative. I'm happy that you now are informed, but there was no reason to say "uhh, i mean a roth. yeah. a roth."

You couldn't be further off the mark. I've contributed to a Roth IRA for years, so I know you're incorrect about the individual contribution limit (it's $5,500 now). I live in the Bay Area. I replied to your comment because I've spent a fair bit of time thinking about this exact situation, and you responded in a rude and patronizing manner. That's not why I come to HN.

My reply was in the context of the $100k earner mentioned earlier, who would not be restricted from contributing to a Roth. Our hypothetical young tech worker is going to expect his or her real salary (and tax rate) to go nowhere but up as the years roll on. It's not bizarre to imagine this person might choose Roth rather than traditional for individual savings, independent of any 401k they might be contributing to.

Oh come on man.

There is only one way to read your comment: "Small correction -- state income tax in CA is a big deal even if you're saving for retirement. And once you retire, you presumably won't care what the state income tax is."

You didn't qualify that! You added a "small correction" that was anything but. And yes, you got me, I didn't realize that for 2013 (possibly 2012?) the Roth limit was increased to $5500. Still not much stacked against the $24,000 I saved in my tax deferred accounts last year.

Listen man, i'm not one for silly debates on the internet, so go ahead and have the last word. But If you're going to add a "small correction" that is not really a correction, you should expect some disagreement.

Perhaps what you really meant was "That's true, unless you chose a Roth IRA as your only form of retirement savings. In that case, current tax rates matter and future tax rates don't."

That still glosses over the fact that I'm talking generally and you're talking about a specific, somewhat rare scenario. But at least it's accurate. As it was, had I not replied to you, a casual reader would've read my post, then yours, and walked away assuming that retirement savings is taxed at your current tax rate, in your current state of residence, when in reality it's just not so.

I wasn't talking about people making $200k, though. I was talking about people making $100k, because that's the number cherry picked by the person I was replying to.

And, yes, of course I'm aware that a Model S is the same price no matter where you buy it, to a first approximation. The point is that housing is so expensive in the Bay Area that you can actually end up having less disposable income left over for your car than someone making $20k less than you on paper in a much cheaper city and in a state with lower (or no) income taxes (Washington, Texas, maybe a few others?). If you don't believe me, you need to just sit down with a calculator that will do taxes and everything, look up comparable rents, and do the math. You sound like you might be surprised.

When people talk about a Silicon Valley "bubble," part of what they're talking about is that a Tesla driver, BMW M5 driver, and Porsche 911 driver can believe that they are "average middleish class people."

When one tiny sliver of society (web engineers) simultaneously wields so much influence (as web companies do) and is so cut off from the reality of America (as you apparently are), it doesn't bode well.

This is so true. I'm currently a student and am sort of terrified to join the workforce in this industry. I really have no desire to surround myself with people who are so ignorant of and inured to the way real fucking people live. As someone who spent the majority of their childhood in poverty and was homeless for an extended period of time, this sort of hubris is profoundly saddening. It's very upsetting how abundant this form of arrogance is in the tech industry.

Luckily, there's a vast, vast array of options other than going to Silicon Valley. Any city decent sized city around the globe will have options available.

Outside of a couple critical mass areas in the US -- I'm thinking SV, greater Boston, NYC (just because everyone there is in their own little bubble ;) ) -- it's just another job.

And if you're not in the US, I wouldn't even know where this sort of SV halo exists.

The average yearly income in the US is $43,000. The base price of a Model S is $63,000. There is simply no way to afford a Tesla as an average, middle-class laborer without making massive tradeoffs in quality of life elsewhere. If you can afford a car that costs such an absurd amount of money, you are either living in squalor to afford it or you are not middle class. It's tiring to see people who are obviously the beneficiaries of economic privilege pretend as though they are "average." You are not, and to assert that you are demonstrates a fundamental ignorance about the difficulties that "average" people face.

As for the house argument, you and I both know that the two are totally incomparable. Putting a roof on your head is a much bigger priority than buying an electric supercar. People need to pay for shelter. They generally can't afford to pay a lot for luxury cars. If you argument is true, why isn't everyone buying $63,000 cars? (Not to mention the millions of people who can't even afford homes.)

Your posts demonstrates everything that is wrong with class stratification in America. I don't think you or your friends who elected to choose Teslas over Porches know what it means to be "average."

I know a local gardener/landscaper laborer in the SF bay area who makes $25 an hour in cash by working after hours. If a Tesla lease is $600 a month (the website says that, but it's based on some assumptions including where you live), he would have to work about five hours a week extra to afford a Model S.

That means this SF bay area laborer must give up a Saturday or Sunday afternoon every week, but it's hardly impossible "to afford" or a "massive tradeoff in quality of life." On the other hand, it's challenging to haul a few thousand pounds of mulch in a Tesla, I expect.

Ok, so if you commit tax evasion in an all-cash business, you too can work just an extra 1/2 week every month to lease a tesla, after factoring in the tax breaks EXCEPT... from my 5 minutes of research, the $7500 tax credit is not a refundable credit so in his all cash business if he's not at least paying $7500 a year in federal income taxes, he won't get the full benefit of that credit.

Oh, and the $600/mo assumes a $7100 down payment, which needless to say is far more than the average down payment on a car and is really more like what the average american puts down on a HOUSE. In other words: c'mon.

Not to mention the opportunity cost of that money. If you're making $25/hr in SF you do not have a high standard of living, especially when compared to your neighbors which, studies have shown, is exactly how we measure our own financial happiness.

In this case, the SF bay area fellow I know works five days a week for a landscape/gardening company and pays taxes on that income. ($25/hour cash is additional off-the-books income.) And, contrary to your research, California has a $10,000 incentive.

Though you're right about the down payment, so let's assume it will be a used Tesla and therefore cheaper. And you're right about the relative comparison point. But these were rough numbers, remember, and not intended to be a detailed argument as much as a refutation of the impossible "to afford" claim above.

Wha? A low-end Prius is ~$20k. A low-end Tesla is ~$65k. The US median household income is ~$45k.

If you can afford to spend the average household's entire annual income on a car coolness upgrade, then yes, you have disposable income to throw around, and no, you're not middle class.

I spent 5 minutes writing a Hacker News comment and even qualified my assumption with the word "probably". At best, I get a bit of karma.

Musk is speaking definitively, and has literally a billion dollars at stake with this post.

My point wasn't necessarily that I'm right -- much like you, I'm just arguing that the logic isn't as simple as it's made out to be.

100 million miles worth of driving is not a small number. After four years with a ~100 mile/workday commute, I put somewhat less than 100k miles on my car. Multiplying that out, it would take me over 40 years of driving at the same pace to reach 1 million miles and therefore well over 4,000 years of driving to reach the number of miles driven by Tesla owners.

So if I drove that 100 mile/workday commute for 4,000 years, something like this might happen approximately once.

Incidentally, I have seen, during said commute, the remains of an ordinary car that caught on fire. There was nothing left but a burnt skeleton of a car that appeared to be made of ashes. I'd rather be in the Tesla while it was still on fire than the burnt wreck I saw.

Your math only works if we assume you're the only driver that matters.

I do not understand your comment. This is the risk, as observed, measured with respect to a single person driving heavily. In other words, most people should expect less risk than this. You are correct that a larger population should expect more risk: there have certainly been more accidents than this overall, and a battery fire is not the only thing to worry about.

But risks must be compared to the relevant alternatives. Certainly, those who arrange their life such that they do not drive at all are removing a significant risk, as I can personally attest to having encountered several drivers who were, frankly, suicidal. I speak specifically of the person who pulled into a turning lane to pass (when I was already in it, stopped), and gunned it driving straight at me. By no means should you think that I am diminishing the very real risk we engage in every day while driving.

But most people measure risk by how easily they can imagine a scenario. As such, I offer this for you to contrast with the photos in the article: https://www.google.com/search?q=burnt+out+car&tbm=isch Such things are not uncommon and I have, personally, witnessed such. While measuring risk according to one's memory is a useful cognitive shortcut in many situations, but with the way our news sensationalizes things by highlighting unusual events and under-reporting common ones, it is not a useful metric.

You cant just compare fires in petrol cars driven 3 trillion miles a year with fires in tesla cars driven 100 million miles a year, its just not very representative. You can either take for example BMW and look up how many fires they had for a new 5 series in 100M miles driven and or let Tesla owners drive 3 trillion miles and see how numbers compare.

Just like Elon did it, it sounds nice but doesnt make a lot of sense.

You are correct that we have a higher confidence in the fire rate for gasoline cars. You are not correct in implying that we have little idea of the rate of fires in Tesla cars. We don't have '1 event' worth of data, we have '100 million miles' worth of data. That aside, yes, we should update our estimates based on future data as it is virtually certain that the numbers will fluctuate. Actually, they already have, based on there being more miles driven and no new reported fires. But few people remember to update their confidence based on a lack of events.

Note that there have been a lot of fires in those 3 trillion miles driven by ordinary cars (not just 1), as even a quick search shows: https://www.google.com/search?q=burnt+out+car&tbm=isch

Yes and that includes all brands, used cars, old cars etc. Like i said, compare that with similar new cars like the new 5 Series or Benz E Series and i would guess numbers would be much closer.

If you have that data, feel free to share it so that we can compare the risk. I do not feel particularly threatened by a 'once in 4,000 years of heavy driving' type of event on a personal level, though if there were any evidence of systemic risk, I might be more concerned, though I do not own a Tesla. I also assume that there is some non-zero risk of a more catastrophic accident, which will then cause further hand-wringing, but I expect it to occur in a crash that was unlikely to be survivable or for it to involve someone doing something completely moronic. Or quite possibly both things at once and then some.

On an individual level, I am far more worried about identifying and avoiding the disturbingly large number of idiotically suicidal drivers I have met. And I mean that very seriously: as soon as I identify someone driving erratically, I find some way to get away from them, whether it means forcing them to pass me, taking an unplanned exit, or what have you, I will make sure I put distance between us.

But I remain unconcerned about a single report of a small car fire when there are many worse ones every single year (if not every day...)

I agree with you. My disposable income is not enough to buy a Tesla, but it is enough for a MINI Cooper. I drive it like I stole it, to quote my mechanic.

"I drive it like I stole it, to quote my mechanic" -> LOL! I would say: "like I'm stealing it" :)

I drive a Tesla. It's a much bigger car and a much more expensive car than my old prius. As such, I am terrified to drive it. I'm neither superior nor inferior of a driver as a result of purchasing and driving a tesla, but I'm certainly more afraid of loss than I used to be -- both the loss of money, and the loss of time I get to spend driving my Tesla should I be in an accident.

Thats interesting. I would have guessed most people would love their Tesla. Do you drive the old Prius instead?

It's funny to hear someone say this. I just went from a Toyota Camry (a relatively big car) to Toyota Prius-C, and I have the opposite feelings. Doing a shoulder check is very hard with the Prius, because of the weird back of the car. I now as a result hesitate driving it a lot, instead opting to use my brother's Corolla.

I do use the Prius in the city though, I easily get 75+ mpg when supermiling.

Your problem may have a solution. A search on "side mirror blind spot" turns up a bunch of products and some helpful advice [0].

[0] http://www.caranddriver.com/features/how-to-adjust-your-mirr...

I love my Tesla. That makes me more terrified to drive it.

I love my 1 year old Son. That makes me more terrified to drop him.

"they have a brand new expensive car"

A good point. It would be interesting to compare the miles drive on "brand new expensive cars" not just all cars which include obviously older and/or poorly maintained vehicles.

Why would that be relevant? Anyone who buys a Tesla Model S will instantly be in the category of "people who buy brand new expensive cars," so the Model S stats are sufficient.

That's the point. larrys wants to compare the Model S miles driven by "people who buy brand new expensive cars" against other car miles driven by "people who buy brand new expensive cars," instead of comparing the Model S miles [...] against other car miles driven by everyone.

This comparison is a bit off. Most of the cars which catch fire are old. The comparison should be to a similarly priced, brand new luxury car. Very few of those catch fire, either.

Well, then I would limit it to Ferraris that are 3 years or younger :).

I think this is Elon's one blind spot. For a engineer he's awfully "salesy" at times. The whole lease thing was really distasteful. This less so; but still a bit awkward. Why not just end with "Fires are unfortunately a risk for electric and gasoline cars. Each year in the US there are more than 150,000 fires. As more and more Tesla's enter the world we're going to experience all manner of events" That would be the right way to put this in context. However, I suspect that to overcome the naysayers and truly change a market (electric cars) requires an almost insane love for what you do - which makes you sound a little too defensive when something goes wrong.

I have no idea how Tesla operates internally, but I wouldn't be too surprised if, like at most companies, letters that go out under the CEO's name are vetted by both the legal and PR departments, and possibly written or edited by them. If that's the case, then "Elon Musk" is a sort of composite entity, which includes a human named "Elon Musk", but not solely that human.

I would agree. But there's nothing in here that's cause for concern legally. And PR folks are going to have a tough time overruling Elon based on "style" points. As I mentioned he probably sees nothing wrong with his approach and thus any PR comments would fall on deaf ears.

It's unfortunate that our current media climate requires it, but a straightforward, "accept the inherent risks" approach to the problem would be massacred by news outlets. Were Musk to say something like this, headlines could read "Tesla's Billionaire Owner Disregards Model S Fire Hazzard" and not suffer libel.

Particularly for people such as Musk, who are doing so much to advance the expectations of consumers and raise the bar for what is possible with new technology (and here I'm speaking as an un-abashed Musk supporter), I can't help but support his rigorous defense of his projects. Whether it's the NYT "review" that attempted to slam the Model S mile range or the astonishingly good crash ratings for the same car, I think it serves us all to let Musk use his soapbox to be an advocate for his work at Tesla, SpaceX, etc.

I dislike that statement, too, but for different reasons.

The 30,000x larger sample in the aggregate means the calculated fire rate for non-Tesla cars is probably a more reliable number. Maybe those 100M Tesla miles were "lucky"? Possibly not, though - I don't know enough about cars to guess.

The 3 trillion aggregate miles includes a lot broader sample size of car age than those from a single company that's 10 years old. This, to me, seems important to control for.

Finally - I bet the usage profile of a Tesla is different from the median usage profile of every random car on the street and throughout the country.

I believe your reasoning is incorrect. If we model the number of fires by a poisson distribution (very reasonable), a single sample would correspond to the mode of the distribution. What you would like is an estimate of the mean, i.e. lambda. It so happens that the mode of a poisson distribution is floor(lambda) or ceiling(lambda)-1, and thus it is an underestimate of the mean. In other words, fires are likely to be less frequent than what a single sample suggests.

Apples to apples: how many car fires are started because the car is old and not in good repair? I'll bet the rate is much lower for gasoline cars less than a year old. We'll just have to wait to see how 10-year-old Teslas hold up.

I'm a big fan of Elon but I think he may be way off with these numbers... :S

If you read the reports from the National Fire Protection Association they do estimate the number of "highway vehicle fires" at around 150 000 per year [1], but they also explicitly say that 'the term “highway vehicle fires” is used to describe the type of vehicle, not the location of the fire' [2].

If you look at fires caused by collision or overturn (which I guess this would be classified as) that's only 4% of the total, or 6000 per year.

1. https://www.nfpa.org/safety-information/for-consumers/vehicl...

2. https://www.nfpa.org/research/statistical-reports/vehicles/v...

According to some quick math, then, Teslas are 9x more likely to catch on fire from a collision than the average US car (1 / 5K) / (6K / 254M). I put the Tesla fire rate at one in 5000 per year because the average Tesla has been on the road for around half a year, and there are 10,000 of them.

I bet you could get the number lower if you only counted fires caused by collision or overturn of a highway vehicle less than 3 years old. Or heck, just the black ones.

Yes, this fire was caused by a collision, but fires caused by other things are relevant. If a Tesla car caught fire in somebody's driveway, people would be concerned about that too, right? So comparing 150,000 highway vehicle fires to 1 Tesla fire, regardless of cause, is pretty reasonable.

In considering whether to buy a Tesla, I would evaluate the safety of the alternatives. Most in the market for a Tesla aren't going to buy the 23 year old Buick LeSabre whose oil leaks caught fire on the Jersey turnpike last week. So I think it's reasonable to compare the safety with a modern luxury sedan. I don't think as many of those catch fire without a collision.

if 100 million miles isn't enough to gain statistical significance, what number is?

I think it's lamentable that we're all looking at the bulk, "brute-force" statistical reasoning instead of considering the details of the case and what that means for the fire safety of the car. The line you quoted was incidental, rather than necessary, to the substance of Musk's argument. Whether it's PR or not is ignoratio elenchi.

If the battery really was punctured by an unfortunately placed piece of metal in a sort of surprising scenario, we ought to stratify by collision type in order to really understand the problem. How do gas cars perform during a gas tank puncture? At similar speeds? And how common are such collisions? The relevance of this consideration is expressed by Simpson's paradox:

http://en.wikipedia.org/wiki/Simpson's_paradox

I.e. analyses of performance when conditions differ ought to take into account those conditions, at least when they are both a: known (true in this case) and b: not causally connected to the variable under consideration (also true in this case).

Mr Market overreacts to bad news, and when a value investor buys.

Agreed, there's insufficient data for meaningful statistics, but his main points were amour-plating, firewalls and that batteries are less fire-prone than "highly flammable liquid".

Also, how many Tesla drivers are driving around in 10-year-old cars? There are plenty of avenues to explore in debunking that statistical hand-waving.

My boat's hull happens to be made of 1/4 inch metal plate (6mm) which is apparently the same as the protected underside of a Tesla. I've hit a concrete block, gone aground a few times and generally have a bit of excperiencing with impacting hard immovable objects with a vehicle protected by a 1/4 inch metal plate.

It takes a LOT of force to pierce 1/4 inch plate. My boat weighs 12 tons, and it hardly has a dent from the collissions I and previous owners have been in.

your point being?

that if a tesla has a 1/4 inch protective plate seperating the batteries from the road it's a safe vehicle indeed.

I was simply sharing my personal experience with ramming 1/4 inch plated vehicles into hard immovable objects to give some perspective as to what kind of strength we're talking about.

The fire in question involved the piercing of a 1/4" plate protecting the battery from below. If that's a thick enough plate to protect a 12-ton boat, which has more momentum than the Tesla even at much slower speeds, with hardly a dent, then the Tesla incident was very, very out of the ordinary.

Tesla's write-ups on their blog are the most informative reports I've seen written by a company about their own product. It's awesome to see this kind of transparency as opposed just a copy-paste statement like "Tesla is investigating the event."

I think the write-up is pretty good.

I would only point that 25 tons of force, isn't really a lot - I mean, the small jack that you use to lift your car can be a 5 or 6 ton device.

You have a vehicle traveling a decent rate of speed, for it to strike or run over anything at all will involve tons of force.

Neat explanation of the sort of math involved, with both SI and US units http://hyperphysics.phy-astr.gsu.edu/hbase/carcr.html . In the example, a car going 30 mph (50km/h) striking a tree will hit with about 48 tons of force.

In both examples that you provided, the cross-sectional area over which the force is applied is greater, so the overall pressure is lower. The magnitude of the force applied isn't the only parameter by which to judge the structural integrity in this particular instance.

> I would only point that 25 tons of force, isn't really a lot - I mean, the small jack that you use to lift your car can be a 5 or 6 ton device.

It's not clear to me why you'd say it's not a lot of force while making the comparison to a jack. Take a jack and use it under the wrong spot on a vehicle and you might get a pretty painful display of vehicle penetration, which is what we're really talking about here.

....yet the jack produces 1/5th the amount of force.

Just to put it into explicit perspective.

> I would only point that 25 tons of force, isn't really a lot - I mean, the small jack that you use to lift your car can be a 5 or 6 ton device.

Floor jacks easily punch through most points on modern cars. In fact, the only place that it is safe to jack up your car are special jack points which are reenforced to bear the load of the jack. The center ones on my car are pretty annoying to get to. Also, your estimate for the ratings of jacks is off by a factor of x2 to x4. Floor jacks, which have a leaver and a hydraulic component, are typically only rated for 2 to 3 tons. Scissor jacks, a manual jack that comes with your spare tire, are typically only rated at 1.5 tons or less.

I think the rare occurance is not a collision with > 25 tons of force, but an upwards force on the underside of the car by an object capable of piercing 1/4 inch plate steel (and not ricocheting, as I suspect most debris would).

A jack, although maybe rated to 5 tons, is unable to pierce the bottom of my car at 25 tones of force because my car only weighs 1.5 tons. I'd have to run over something at speed that angles upwards after I drive over it, or drop my car onto something sharp (at 35km/h) to achieve a similar force.

Rate of speed?

I am quite sure much of the driving public never would have thought a battery powered car could go up in flames. That might be the real damage here.

Regardless of Musk's statement, a gasoline powered car would not have suffered a fire most likely in this incident as its fuel source does not stretch to the front of the vehicle. More than likely the debris would have done some serious damage to the underside of the car, if any. There is a lot of open, hollow, space in the underside of most modern cars.

He is handling it wrong by trying to tell people that this car fire is not anything special. Seeing that the fire department had to do quite a bit to contain it means his cars will burn to the ground just like any gasoline car will. I doubt any fire will leave the car in any state but salvage.

It looks like they're backing off the claim that the fire was contained to only one cell. It's unclear, but if the fire were contained to only one cell, it's likely they would mention it:

"A fire caused by the impact began in the front battery module – the battery pack has a total of 16 modules – but was contained to the front section of the car by internal firewalls within the pack."

If the fire was able to jump cells, does this make the battery pack "fundamentally unsound", as Elon has described the Boeing battery? Not necessarily. However, merely puncturing the gas tank of a ICE car in this way is not guaranteed to set the gasoline on fire. The ignition temperature of gasoline is over 500 F and the gas tank itself is plastic, most likely. Gasoline vapor is explosive, but the car was traveling fairly rapidly and a there's a fair amount of wind to dispel vapor. The ignition source would have to be heat from the metal of the debris self-striking metal of the debris, or though both layers of plastic to the auto frame itself, and that spark would have to find some gasoline, which is pooled at the bottom of the tank and not near the top. I suppose it's possible. Car crashes do produce burning gasoline, though usually it's a very severe crash that mixes gas vapor with the heat of the engine.

I also wonder whether the surface area that, if punctured, poses a fire risk is larger on a Tesla than on a gasoline vehicle.

within the pac

This is worth noting. The fire did not stop and kept reignighting. The FD had to flip the car on its side and physically gain access by cutting the car up, to put the fire out. Under this scenario, it seems dubious that compartmentalization would be sufficient. Thermal conductivity at some stage would overcome the situation.

Also, you are right to highlight that petrol fuel systems are a cause only on a tiny minority of real-life auto accident related fires (~2%). The safety of petrol engines is actually quite high in this regards (counter-intuitive, perhaps). Plastic has the ability to deform rather than crack (flexibil vs brittle) and also the position of the fuel cells is much more protected. Think about the debris from front-tires -- much more likely to hit the undercarriage (where the Tesla battery is) than behind the rear axel (where many tanks are). Debris hit by the rear tires of course exits behidnd the car in either scenario. This setup is obviously not by chance. The Li Ion battery is probably low for COG reasons and fore-aft weight distribution. Li ION is much heavier than petrol.

Question: Is it really that unusual to have 25 tons of force applied to a point of the underside of the car in an accident? Does anyone know?

My conjecture: The Model S is a heavy car. Hit something pokey at speed and you've got an awful lot of forces channeled to a point.

I also thought it a bit much that Musk tried to compare this to severing "fuel supply lines" in a gas car. The likelihood of a 3 inch puncture severing a fuel line or entering the gas tank is vastly lower than compromising a battery pack that runs the length of the underside of the car.

The Tesla's underbelly vulnerability zone is vastly larger than fuel tanks and lines.. and a punctured battery doesn't need an ignition source to start a fire, either.

Looking At some pictures and diagrams of the Model S battery pack, yes, it does look to be about twice as large as the average fuel tank. HOWEVER, that leaves out some really interesting things to note.

First of all, most automotive gas tanks are made out of ~1/8" HDPE. While it has decent cut and abrasion resistance, it's of virtually no use when trying to combat punctures and is also pretty flimsy, leading to deformation and possible cracking during an accident.

While, yes, a punctured battery pack is guaranteed to ignite while a gas tank is not, that is also the only way for the pack to ignite. An object has to physically pass through the battery pack, while a gas tank could potentially start a fire if it cracks and starts leaking. There's a reason why you're supposed to try to get out your car as quickly as possible in case of a crash: fuel leaks very easily. In comparison, batteries are much more impact resistant due to their more solid state nature.

Also, it seems that whatever struck the car seemed to hit under or very close to where the front passengers sit. Had that armored battery pack not been there, there's a very real possibility that the driver would have been impaled. With that in mind, it should be pretty clear that this was a freak accident and not really representative of the average car crash.

Is Elon's claim, "the effective combustion potential is only about 1% that of the fuel in a comparable gasoline sedan", accurate?

AFAIK, all the Lithium Ion Battery electrolytes are flammable (they are pressurized in the battery container too). Depending on the chemistry of the Lithium-ion battery that Model S uses, some (I.E. LFP) are safer than the others, but still, 1% potential?

EVs like Chevy Volt, Fisker Karma and even Boeing 787 Dreamliner and UPS/FedEx freight flights had been caught Lithium fires in air before.

Wasn't there some controversy about Elon saying the Dreamliner specifically didn't have the right kind of firewalls/compartmentalization and that Tesla could help them?

Yes. http://www.reuters.com/article/2013/01/29/boeing-tesla-idUSL...

  In contrast, the combustion energy of our battery pack is only
  about 10% of the energy contained in a gasoline tank and is
  divided into 16 modules with firewalls in between. As a
  consequence, the effective combustion potential is only about
  1% that of the fuel in a comparable gasoline sedan.

It seems he's dividing that 10% by 16 and rounding up based on his confidence (presented confidence or real confidence I don't know) in the firewalls.

In making that claim he's presumably assuming that the battery design prevents a cascading failure where the failure of one battery module causes adjacent ones to fail in turn. He's also assuming that there's no external factor that could cause all the battery compartments to fail simultaneously. It's partially PR fluff in other words.

The total combustion energy of the battery pack is only 10% of that of the petrol tank in a petrol-fueled vehicle partially because the energy density of Lithium-ion cells is significantly less than petrol or diesel fuel, which is why the Model S has half the range of similar conventionally fuelled cars in it's class. I'd also speculate that he's only measuring the combustion energy of the hydrogen that could escape & ignoring any electrical heat generated. The control systems on the batteries ought to cut the connections to the cells if they detect a short of course, but no system is perfect & he's very careful to use the more specific term "combustion energy".

> In making that claim he's presumably assuming that the battery design prevents a cascading failure where the failure of one battery module causes adjacent ones to fail in turn. He's also assuming that there's no external factor that could cause all the battery compartments to fail simultaneously. It's partially PR fluff in other words.

Maybe. When the dreamliner battery fire happened, had quite a bit to say regarding batteries and cascading failure. He's surely making some assumptions (such as discounting an external factor as you state), but it's not like he isn't on record asserting they have put some effort into preventing or mitigating this exact problem[1].

[1]: http://www.dailytech.com/Tesla+CEO+Elon+Musk+Says+Boeings+78...

It's a 85kWh battery (http://en.wikipedia.org/wiki/Tesla_Model_S#Specifications).

Gasoline is about 12kWh/kg or 9kWh/l (http://en.wikipedia.org/wiki/Gasoline#Energy_content)

So, that 85kWh battery, when driving an engine, is equivalent to about 10 liters of gasoline. I guess that's more or less what could get released in a fire (corrections welcome; I don't know what kind of factor that 'effective' could introduce)

If that logic stands, to get at 1%, the typical car would have to have 1000 liters of gasoline on board (for the metric impaired: that's over 250 US gallons/over 200 imperial gallons). That, clearly, is unrealistic.

Elon may have knowledge of the loading state of the battery, but if so, I think he should have mentioned that. Gasoline tanks aren't 100% full all the time, either.

> Gasoline tanks aren't 100% full all the time, either.

The less gas a tank has, the more dangerous it could be. It's a common mistake to think a close to empty tank of gasoline is safer than a full one when the reverse may be true because of the fumes.

For example:

http://www.commerce.wa.gov.au/worksafe/content/safety_topics...

We're just talking about energy content right now, not damage potential.

I'm not convinced of that. If you are worried about the tank going "pop", then a mostly empty gas tank would indeed be more dangerous. However I think the more typical concern is the tank being punctured, leaking, then the leaking gas burning rather than exploding.

So basically if you want it to explode hollywood style, then you need gas vapors, but if you want a very bad car fire, then you need lots of gas.

it isn't much of a data point, but when the fire brigade turn up to a car fire they first thing they ask is about how much fuel is in the tank. The less there is the more worried they are. I've been in the situation twice. Presumably an explosion is more worrying than big flames.

Ehh, I mean, they already know there is a fire and that fire getting bigger is something they anticipate one way or the other, but an explosion could take them by surprise.

I suspect that more people are killed by big flames than explosions, but more fire fighers are killed by explosions than big flames.

If you want a very bad car fire, then half of your current tank is plenty enough and even overkill.

Lots of gas can do much more - say, if a gas lorry spills under a concrete bridge, then the fire can do structural damage to that.

No; as he states in the article, the total combustion energy of the battery is approximately 10% of the equivalent gasoline vehicle. However, as the battery is divided into 16 modules with firewalls between them, the probability of more than one igniting in a cascading failure is significantly reduced.

Just like the Titanic!

Hmm, I wonder if a "scrape along something very hard" type of accident could cause the failure of enough cells to cross the firewalls into the other cells...

You are missing the divide into 16 isolated battery modules.

Two things.

1. I have had my gasoline car catch on fire in my lifetime. (That was the end of the car.) However, it was having a lot of trouble at the time and we had just taken it to the mechanic. (That's right, it caught on fire at the mechanic's shop. We were still waiting to talk to the mechanic before going back home when it caught on fire.) This was not the only on-fire incident among our friends. One had his minivan catch on fire in a gas station.

But both of them were old cars. What is to say that most of the cars that catch on fire aren't much older than the Tesla? What is to say that the Tesla won't have more trouble as it gets older?

Oh yeah. The batteries will have to be replaced before the car is run down as much as our old beaters were. And Tesla owners will have the money to maintain their cars better than we did as teenagers.

So, what I'm saying is that the real test will be in a decade. More fires will probably happen, just like regular cars do.

Either way, it's probably not dangerous enough to be worth avoiding buying a new one.

Curious as to your reasoning on saying that the batteries will have to be replaced before the car is as run down as your old cars. So far evidence is pointing towards batteries lasting much longer than originally thought. How old were your cars?

They still HAVE to be replace whereas a 30 year old car can continue to run a Teenagers budget

We're talking about 15-20 year old cars.

I really don't care about "it would be worse if it were a gasoline powered vehicle". That statement is simply trying to redirect attention. Leave statements like that out of the problem diagnoses and simply concentrate on what went right.

Otherwise it looks like making excuses and that is bad.

It wouldn't have been mentioned if it wasn't already the main discussion going on about the video. News outlets love to jump on that kind of controversy, and I saw that comparison as them trying to quell the argument.

To some extent the comparison needed to be made based on the media reports calling into question the overall safety of EVs based on this incident. The closest equivalent for conventional vehicles is a gas fire so pointing out the (apparent) greater danger makes sense here.

Perfect safety is not attainable, and this is especially true when it comes to automobile travel, which is probably the most dangerous activity that most first-worlders engage in on a regular basis.

Much of that danger is inherent to the way the system works and the current level of technology and the costs people are willing to pay. A single car maker will never be able to get anywhere remotely close to airliner levels of safety.

That means that Tesla's products will be used in dangerous circumstances, and Tesla customers will die while using their product.

For a normal car company, this would not be a problem, because the public accepts the current risks of automobile travel. The problem is that Tesla is Different and gets far more scrutiny.

Tesla needs to convince people to accept the risks inherent in using their products. Pointing out that people accept the even greater risks inherent in using their competitors' products is a perfectly reasonable thing to do.

I think it's pretty relevant. The car was in a bad accident that no car would survive. Had this been a gasoline vehicle, the damage probably would have been much worse and there would have been a higher chance of the passengers getting caught in the fire.

How is saying that it would be worse with a gas vehicle an excuse? The point seems very relevant, since the primary differentiator of Tesla cars is that they are electric.

Redirect from what? The fact that motor vehicles are incredibly unsafe compared to other means of mass transport (trains, planes)?

Fact is, there are thousands of people who die every year in motor vehicle accidents. Gas tank leaks and fires are a nonzero portion of those accidents.

A battery fire, especially one where the driver walked away unharmed, is only news because it's the first one for Tesla. How is putting things in perspective to be construed as redirection or deflection?

In the meanwhile, Car companies are notorious for denying anything's wrong: http://www.southcarolinalawyerblog.com/2013/06/chrysler_refu...

Initial attempts to douse the fire were unsuccessful. “The fire appeared to be extinguished, then reignited underneath the vehicle,” the report said. Firefighters had to use a jack to turn the Model S on its side, and then cut a hole in the car to apply water to the burning battery.

He seemed to skip that last bit. (?)

I have seen videos of normal gasoline car fires that behave the same way.

What did they use to cut the hole in the gas tank with? Just curious.

A little closer reading of the report[1,2], shows that only 26,000 automobile fires occur on public highways. That makes Tesla's single datapoint worse than a conventional Auto.

All cars: 1 fire per 116 million vehicle miles/year

Tesla: 1 fire per 113 m vehicle miles/since inception

Obviously, the Model (s) being a newer Tesla model does not have the full historical amount of "Tesla" Miles as the denominator.

[1] http://www.nfpa.org/~/media/files/research/nfpa%20reports/ve...

[2] Furthermore, only 2% of non-deliberate fires start in the fuel line or fuel tank of a normal vehicle

Wow, first serious Tesla road accident and all they can say is how unlikely it was. It was impossible before, now it's only extremely unlikely. Until next time? There are probably many other ways to destroy the battery in a collision, how likely is it to ignite when damaged?

It was never "impossible before". Just two months ago when writing about Model S's safety rating, they stated that it was unlikely to remain the case forever that a Tesla car has never caught fire or caused an occupant fatality.

They've always published First Responder fact sheets for their cars which talk about how firefighters should handle a battery on fire.

http://www.teslamotors.com/sites/default/files/downloads/201...

There have been many more serious road accidents with Teslas. Just ones with more mundane causes.

As much as I admire the work Tesla and Elon Musk are doing, I can't help but feel that the press releases issued by the company are at times overly defensive.

We all know there is negative rhetoric bouncing around about this incident. It seems to me that, precisely because of this, there really isn't a need to write in such a manner—trying to block all possible avenues of attack as if one is a afraid of what will be written in response.

The tone, to me, betrays insecurity, and this seems something at odds with the bullish, innovative nature of the non-PR aspects of the business.

The following statement is wrong at many levels.

- All Tesla cars are new and almost all of them have superior drivers.

- They drive their cars only on certain roads where as Gasoline cars are almost everywhere.

- You can not compare 100m sample set with 2 trillion size sample set.

And he forgot to mention many gasoline car fires aren't due to gasoline ignition, but electrical failures or material melting (plastic/glue), etc. The only common case of gas ignition is static electricity while filling up, f.ex. re-entering the car while wearing a sweater (you can even smoke a cigarette while filling up, it's the spark that's dangerous). Closed gasoline tanks have been safe for decades and contrary to what we see in movies it's close to impossible to fire them up even in serious car crashes, especially when they're full. There is even a method for extreme freezes (-30-40'c) to light a small fire under the tank to help the fuel flow to start the engine (especially needed for diesels and low quality gasoline) and the only fires due to that are when the stupid owner didn't realize his tank or other parts around are plastic (which's quite a modern day problem).

Excellent post-mortem!

And who would have thought a side-effect of disrupting the automotive industry would be training fire-fighters on the correct techniques for battling a lithium fueled fire?

I wonder what he means by 1/4" armor plate - AR500? Is it actually rated for armor plating, or just built with material from which you could also build rated plates?

Why are people on HN so keen on defending Tesla at all cost?

The title is missing word "incident". My first thought was that Tesla has a new model "S Fire".

A car called Model S Fire would be like a software package called Microsoft Crash.

So a truck driver who couldn't be bothered to secure his fucking load just cost Tesla shareholders $1b+?

No, jittery shareholders transferred $1b+ to their less anxious peers.

And got an opportunity to double down.

Maybe speculative, short-term shareholders.

I haven't seen the debris but it could have been part of the trailer itself. Not that it makes it any better. Things should not be falling off of trucks. Just saying that it might have been a maintenance issue or some kind of freak accident.

That being said, If that part had punctured a gas tank of a petrol vehicle the damage could've been explosive or caused a fire also.

I like how they have calculated how this happened because that most likely means in the next revision they may improve the skid plate or the battery wall to protect it from such things. Or recall them and retrofit, if needed. They aren't being mysterious like I've seen from other auto manufacturers. But then again, not every company dives in $1B in worth after a car has an accident.

I wonder if break-away would make sense.

In liquid form, gasoline isn't all that excited about exploding.

Mythbusters did it:

http://dsc.discovery.com/tv-shows/mythbusters/mythbusters-da...

Yes, but a car/truck/van will turn into a ferocious little bonfire given the right kind of damage, an ignition source, and time.

Sure, I was responding to the scary emphasized word.

IRL less than 2% of auto fires involve fuel lines/tanks etc. Your scenario tends to play out better for intentional fires, tho. So, yeah if you molotov cocktail a car it will ignite...but it does not do so under typical use hardly ever.

source: the same one Musk quoted.

Yeah much like a lot of substances it's only explosive in vapor form. I was thinking the top part of a gas tank, some hypothetical, but not likely, scenario. It seems that the danger from both the Lithium battery and a gas tank are about the same. If the car catches fire it will be because of some freak accident.

Although, there was the Pinto, which was just poor design: https://www.youtube.com/watch?v=qZDVqhWGILA

Mythbusters tested the "shoot a car's gas tank and make it explode" myth. A punctured gas tank may not explode... but it will leak. And a puddle of gas on the ground around the car can catch fire more easily. And then things get worse from there.

Just because it happens in movies or television doesn't make it real. Cars don't explode.

Then there's this: http://articles.baltimoresun.com/1993-03-23/features/1993082...

Cars can explode after a terrible impact, it's been recorded before. I don't think a gas tank puncture would cause it unless it was some how ventilated, the gas vaporized, and then ignited.

But I know what you mean. You mean the hollywood explosion. That's not real life.

Cars don't generally explode. You need a mix of fuel and air to burn, so most of the gasoline in the tank can't burn at any given time.

I don't have numbers on how much force a typical skid plate can withstand without damage, but I would be willing to bet that 25 tons of force at a relatively small point of impact would be extremely hard to design around without some major drawbacks (weight and ride height, mostly). Considering this is such an uncommon experience. designing for such an edge case and accepting the drawbacks might not even be acceptable.

It sounds more like they're congratulating themselves on designing the failure to be so easily contained.

Jesus! I misread and saw 25 pounds not 25 tons. Yeah, a skid plate would not protect from that I'd imagine.

Or rather, gave some of us the opportunity to buy more TSLA at a ~$20/share discount.

When a stock reacts this dramatically to a chance event like this, it's safe to assume a good portion of the "value" that was lost was speculative in nature, which is not quite the same as losing real value.

Am I the only one to see the parallels with the Concorde accident, where a piece of metal dropped by a Continental flight was the main culprit[1]? Is it because of (bad) American haulers that we can't have good things?

[1] http://en.wikipedia.org/wiki/Air_France_Flight_4590

I wish Elon would do a supersonic point to point transpacific service next, maybe through spacex. Going to space is nice, but flying from SF to China in 30 minutes would actually be useful.

Virgin Galatic is probably closer to getting that done. IIRC, Space Ship Three is suppose to be for exactly that.

If Toyota owners got one of these emails every time one of them caught on fire it would be sort of a downer, so I guess you only have a few chances to make it a PR event.

I've blogged a fun writeup of the math in the (unimportant and actually against Tesla) formal bias in evaluating a failure rate right after the first failure: http://www.win-vector.com/blog/2013/10/estimating-rates-from...

"Had a conventional gasoline car encountered the same object on the highway, the result could have been far worse."

Diesel-powered car would be much safer, since oil requires something like a wick in it to burn. It's hard to argue with Tesla's statement, since argument is true; but it doesn't include this issue in electric vs ICE vehicle competition.

> This means you are 5 times more likely to experience a fire in a conventional gasoline car than a Tesla!

I LOVE THE COMPANY. I DON'T ENJOY OR APPRECIATE THE LAME MARKETING ATTEMPTS THEY SOMETIMES MAKE. Just like that whole business of jumping through hoops to make it seem like there was some new magical way to finance a Tesla, this is wrong.

Trying to create a safety metric by comparing the number of fires to the number of miles driven per vehicle type is pure nonsense. You have to look at the causes and mechanisms of the fires and dig a lot deeper than that in order to even hope to generate a meaningful metric.

Here's an imperfect analogy (numbers made-up): One million people run marathons every year world wide. 1000 have heart attacks and die. Ten thousand people have run marathons with our shoes and only one had a heart attack and didn't die. You are far less likely to have a heart attack and die if you run marathons with our shoes.

Nonsense. Right?

RIGHT.

Almost anyone would look at that and recognize it as a poor attempt to create a nexus where one does not exist. I think it's bad marketing.

Now, if we started to dive into the statistics and identified location, weather conditions, age, physical conditioning, pre-existing conditions (heart problem they did not know about), etc. we might actually be able to attempt a comparison between people wearing the new shoes vs. the other brands. Even then, the nexus would be tenuous at best.

A similar exercise would be needed to compare car fires between brands and types with any degree of validity. I don't have the time to dive into the stats. It was easy enough to Google [0][1][2][3] and do a quick scan:

It is easy to see that young males are more likely to be involved in a car fire.

There are statistics about different brands having different fatality rates (not necessarily related).

Lots of fires are caused by running equipment. Lots of fires originate in the engine compartment. Mechanical and electrical failures seem to account for over 60% of fires.

The point is simple: Far more extensive and detailed statistical work needs to be undertaken before anyone can conclude absolutely anything on the merits of any particular car or design as it pertains to potential to cause fires.

Elon and his team are very smart. They know this. And this is why some of their marketing of late feels really dirty and beneath them. This is Tesla reacting to news that affected their stock price and, potentially, buyer sentiment, with marketing rather than the truth.

Are Tesla's safer than all gasoline cars? That question is probably not an easy one to answer at all.

There's the potential for a theoretical sort of an answer based on design. For example, there are no fuel lines to rupture. Does that mean it is safer? Hard to say. What do you compare that to? Perhaps you can list all the potential sources of ignition and sort them by probability and MTBF? Not sure.

Of course, then you have the real-life probability. Once you get a million cars on the road with all kinds of people, driving in all conditions, roads and levels of maintenance and neglect things can change dramatically. If I remember correctly Tesla has somewhere in the order of twenty thousand. There's a reason we see major car companies recall hundreds of thousands of cars every so often. Shit happens. Design error are made. And it can take time and a massive installed base to discover them.

THE TRUTH OF THE MATTER is these are the kinds of tests electric cars will have to endure over a period of time in order to reach wide adoption. Despite what's been said here a full tank of gasoline is far safer than a fully charged battery pack with enough energy to go 300 miles.

Before anyone mauls me, consider how many gasoline cars have been driven and, yes, crashed, world-wide since gasoline cars came into mass production. Not last year. Since forever.

There have probably been millions of accidents without fires, even with fuel leaks. There's probably no imaginable way to compare the two at this time. We simply don't have enough data. And, no, linking to a horrible crash video on youtube involving gasoline igniting does absolutley nothing to support arguments on either side.

The one issue with electrics that is not spoken of is the fact that you have a several hundred volt high energy system that could very well electrocute passengers. I fully expect that to happen one day (in general, not necessarily Tesla). If and when that happens you can bet it will set the breaks on electrics for a while and relevant stocks will plummet.

I still believe electric cars are the future. We simply need to go though the evolutionary process that will make them really safe for hundreds of millions of electrics to share the road. What happens when you have a pile-up of ten or twenty electric cars on a fogg-covered highway? A pile of mangled wrecks with 400 Volt high energy systems is unimaginably dangerous. I can think of a few horrific scenarios under those conditions.

At some level part of me thinks that fuel cells are the future, not batteries. Having something relatively benign that can leak out would be a good thing.

A few months ago there was a horrific crash in my neighborhood. This 18 year old kid decided it was OK to go 100 miles per hour on this avenue. He lost control and plowed into a bunch of cars parked by the side of the road. He absolutely destroyed seven of them before coming to a stop. Most of the cars were mangled beyond recognition. He was driving an SUV with a lot of mass. His SUV was nearly cut in half and impaled into one of the cars to a degree that made it difficult to see where one car started and the other ended. Almost like taking two lumps of play-doh and mixing them together.

No fire. Gasoline all over the place but no ignition at all. He hit the first car, fused into it and the "ball" formed by the two cars proceeded to destroy the other six. Absolutely amazing display of how much kinetic energy was dissipated.

Had this been eight fully-charged electric cars I am almost certain there would have been a horrific fire as well as the potential for absolutely impossible to describe electrocution of some of the passengers. And, to make matters worst, it would have taken the rescue crew far longer to remove the victims as they would have to be worries about electrocuting themselves and the victims (at the very least).

Until there are enough electric cars on the road to have a massive pile-up accident [4] where most cars are electric we will not really understand the practical reality of a world where every car on the road is electric. Imagine having to walk out of a one hundred mangled car pile-up where every car has a battery pack storing enough energy to drive 300 to 400 miles and they are wired to produce hundreds of volts. I can't imagine anyone who understands electronics and electricity that would tell me all would be well after looking at the pictures from this accident [4] if all cars were electric. Look at pictures 1, 8 and 11. No fires. Gasoline isn't all that bad in this regard.

[0] http://www.usfa.fema.gov/downloads/pdf/statistics/v13i11.pdf

[1] http://www.usfa.fema.gov/statistics/reports/vehicles.shtm

[2] http://www.chandlerlawgroup.com/library/national-vehicle-fir...

[3] http://www.statisticbrain.com/driver-fatality-stats-by-auto-...

[4] http://www.cnn.com/2013/09/05/world/europe/uk-huge-chain-rea...

Thank you. I'm ranting for the same reasons as you, but didn't have the energy to explain it that comprehensively. That quote is such blatant propaganda I had to check twice if it's actually Elon's post, sad to see him engage in bullshitting.

Fuel tanks/lines and related systems cause only ~2% of Automotive fires in the US (excluding intentional ones).

I wrote a blog post on this last night (Tesla model S and the three laws of robotics).

http://justink.svbtle.com/tesla-model-s-and-the-three-laws-o...

Stakes are high, for sure

Elon Musk & Tesla would review its design, would possibly add protection for these type of accidents.

Will any other gasoline car manufacturer be willing to participate in such crash test what model S encountered, I doubt anyone will.

wow. reading their report always inspires me to be a better engineer

Totally thought this was a name for a new model S model, a la kindle fire.

Tesla, recall is coming, that is obvious. You will be forced to put in stronger armor underneath. So drop the price by $10K, or do the recall sooner. Either way that is the reason for the stock hit, people know one or the other or both are coming.

> "highway speed"

crafty writing. read it as "high speed"

"highway speed" is a fairly common term for the general 55-70mph range. For example, apparently the instructions to have the emissions testing system on my car become "ready" after a battery disconnect involve "at highway speed" for a half an hour or so (I learned that one last week. Fun times.)

He is just great

Downvote me for my opinion you HN haters bring it on

Fire happens. Maybe Tesla performs better, maybe not but cars do catch fire. I, however, will not be buying Elon's explanations simply because he seems like a cheesy salesman and a media whore. http://www.bloomberg.com/news/2013-04-02/tesla-to-begin-mode...

(Knowing the Elon is the Sun God among many here, I want to say this: I do not particularly care about karma, I'm saying 100% of what I am thinking.)

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