Why are cars designed to be capable of going much faster than the speed limit?
theguardian.com
theguardian.com
Acceleration ability is needed and valued. Good acceleration is needed to safely execute a lot of manoeuvres: especially overtaking on a two-lane road with oncoming traffic (more acceleration means less time and distance facing oncoming traffic), and entering a highway (less risk of high speed differential when merging). Again, higher engine power is needed for good acceleration. Indeed at cruising speed, only a small fraction of "power capability" is utilized; short bursts of acceleration are the only time the engine is used to its full extent. Lots of engineering goes into making car engines capable of these short high-intensity sprints, but with low fuel consumption the other 99% of the time.
With today's electronics, you can use very smart feathering off acceleration curves, soft speed limit overrides for overtaking, etc.
Gearing doesn't make sense. I can keep higher RPM but turn cylinders off to reduce power and cap the consumption and speed if I'd like to, but it's not implemented.
Why not add a 6th, 7th, 8th, 9th or 10th gear? Wait, modern transmissions do.
Generally 8 gear systems are paired with ~1.5L force induction engines to keep them in a very narrow RPM band, similar to Diesel engine dynamics. However, speeds nearing 180 KM/h is a natural result of these mathematics.
What I was proposing to keep the same engine, reduce the gear count to 5-6 and keep engine RPM around 2-3K which maps to 90-120 KM/h band generally.
You'll either keep 8 gears with closer ratios for a smoother acceleration, or shave two gears from top, because 8th gear on 120KM/h results in RPMs too low for the engine (on the cars I have driven though).
"Why doesn't trillion dollar industry with millions of engineering hours devoted to optimizing performance just do X, Y, Z?" is classic HN.
Also he asked a question
If you're trying to be generous, which you should be.
Thanks. Actually I know about cars more than I show for reasons I won't detail, but I wanted to people to voice their opinions on the matter.
Having prejudices about people without asking them proper questions is so classic HN, too.
Some vehicles do come with built in speed limiters.
Trucks, vehicles used by delivery companies etc will often have speed limiters; presumably it lowers their insurance?
And some production cars offer them as well. As I understand it, this allows them to scam the emissions/range tests, because no matter how easy to disable or how rarely used the speed limiter is, so long as it leaves the factory with the 60mph speed limiter enabled, then it goes through the emissions tests with it enabled.
I use cruise control and speed limiters regularly, otherwise.
eg. a "W" rated tyre is 270kmh max rated, so the manufacture might set the max vehicle speed to 250.
Tyres get exponentially more expensive as speed ratings go up.
In this case, try enumerating who would govern, and what each possible actor might do to govern, or suggest to govern. There's a tree of options.
For example, it might be a single car manufacturer, and might introduce the limit either globally or in some region. Or it might be a country, except not, because if it's a country it has to start with a department of the state or with a political party. If it's a political party, it can be in government or opposition. The tree is deep.
I'll do one of the leaf nodes: A political party that's currently in government, including the relevant minister if there's a coalition. Such a party has to put forward a concrete suggestion, perhaps a hard limit 120km/h with mandatory 100% responsibility for any accidents if the limited is modified, with supervision by forcing the navigation and mobile phone companies to report user locations. Or it chooses some other concrete proposal. It doesn't matter, because whatever it is it'll get a collection of shitstorms about the concrete details.
The people who think 120km/h is too high would flame it for having an obviously wrong speed limit, the ones who think it's too low would do the same, the data protection/privacy crowd would flame it for the big-brother-ish data collection (but without that, another crowd flames it for lack of enforcement), and so on and so forth.
That a particular change is generally desirable doesn't imply that there exists anyone that can put forward an actionable proposal. Making the change actionable means providing concrete details, and those attract shitstorms.
(On a semirelated note: a politician, a sometime finance minister of a large country, struggled for 10+ years to push through a worldwide reform that most people would consider good. The reform was put into force this year. I haven't seen that politician's name in any reporting in the past year.)
German here. I don't understand the question.
A quote from the inquiry. Other than that the speed limit is not universal, and it's not 'the speed limit' as the limit is context based. There are many a situation where speeding up would help prevent an accident.
So, YMMV.
I guess the issue is when the joke isn't that funny and perceived as too manipulative, and anybody's threshold is different on both those.
> Why are cars designed to be capable of going much faster than the speed limit? (Don’t tell me they’re made with the Autobahn in mind.)
Since you didnt read the question, it was questioning whether the autobahn is a valid reason for the majority of cars and if there was a better reason.
Even with 140km/h in mind, you'd not want to be the absolute upper limit as that would make it inefficient in different ways. If it's about having an artificial limit (say electronics) it could also be needed to temporary speed up over the max. Such a limit would stimulate over inflating the tyres to 'cheat' it.
I would also show the relationship between top speed and engine power. I don't need to drive at 200mph, but I like that I can drive up a hill with 4 adults in the vehicle.
My wife's car has a smaller engine, lower top speed and struggles with more than 2 adults, and 2 children when dealing with hilly countryside.
Last summer I topped out at 210 km/h in my Audi A3 which was bought in Spain, and it seemed to be limited by the engine rather than a hardcoded limit (slowly approached 210 km/h instead of reaching it and then getting stuck there)
But not all are.
> Premium automakers are quietly abandoning their informal agreement limiting the top speed of production cars to 250km/h.
https://www.just-auto.com/news/germany-car-makers-dropping-2...
Maybe it's not a thing anymore?
Even on the autobahn, you'll very rarely see anyone exceeding 3×10⁸ m/s
But for cars, killing and maiming millions a year, no one wants the same. So weird.
There's a whole playbook of strategies for this, developed by tobacco and oil companies.
And then there’s courts. If courts can force drunk drivers to add ignition interlocks to their cars, they can throttle the engines of chronic speeders too.
Standard Tesla feature.
> Apart from the speed cap, every Volvo car will now also come with a Care Key, which allows Volvo drivers to set additional limitations on the car’s top speed, for example before lending their car to other family members or to younger and inexperienced drivers.
[1] https://www.media.volvocars.com/global/en-gb/media/pressrele...
I’m not saying it happens often, but I’ve had times when driving on the motorway when I simply need to accelerate past the normal legal limit to get some distance or swap lanes safely to get away from some one behind me or next to me.
You should start funeral planning if you buy the kid a Chevrolet Spark, with its 0-60 of 11 seconds and top speed of 90mph.
I didn’t use any hyperbole about the fastest car, with highest acceleration, I was merely pointing out that a hard cap at 65mph is (imo) a silly idea as there’s many reasons you would need to accelerate beyond that to get out of an unsafe situation.
I could maybe advocate for a happy medium here, something like a black box given by your insurance company (they already do), insurance premiums for larger, more powerful vehicles being higher (they already are), traffic calming measures, or speed cameras (already exist) and punishments for speeding such as fines, points, bans or additional speed awareness courses (all already exist). If you’ve any additional input here, other than ‘plan a funeral if you don’t limit your kids speed’ then I’d appreciate the discussion as these things clearly don’t fix all the problems that we encounter on the road, but they certainly prevented me from being a dumb ass on the road when I was a teenager, and still manage to.
I trust you weren't using "devil's advocate" as a way to say something while trying to avoid direct criticism.
If 65 mph is too low, then what maximum speed do you think is appropriate? 70? 90? 120? The local maximum speed limit + 15mph?
If you think any artificial limit is intrinsically less safe (bear in mind that high-end cars are already artificially limited to 155 mph), then the same logic says that, if price is not any issue, it's always safer for a kid to drive a faster car with good acceleration - the faster and more powerful, the safer it is.
If you think a maximum of 90mph is too slow to be safe, what do you say to parents who buy their kid a car with a max speed of 90mph? Do you tell them you think that care is unsafe and they should get a faster car if they can afford it?
(This reminds me of the Swedish A-Tractor, which lets 16+ year olds drive certain vehicles so long as they are limited to a max of 30km/h, including through electronic limiters. According to you, that's more unsafe than allowing faster speeds. Strange that the Swedish government feels otherwise.)
Your examples were all on the motorway. I presume a parent wanting the 65 mph speed limit will also want the teen driver to stay off the interstate, motorway, or other highway. If the kid is only supposed to drive on roads with a max 45 mph speed limit, then a car limit of 65 mph should be just fine, yes?
Many US states limit school buses carrying students to 55 mph, even on the interstate. Buses also have lower acceleration than a car. From what I can tell, the consensus by the relevant authorities is that raising the limit to better match the flow of traffic is more dangerous because of the increased deadliness of any crashes.
How is it that the driver of a 15-passenger school bus is able to handle restrictions you think are so unsafe that you couldn't handle them?
I don't understand the point of your last paragraph. Just because those things helped keep you from being a dumb-ass driver as a kid doesn't mean that another tool - a speed limiter - can't be an additional useful parental restriction on a beginning driver. For one, unlike everything you listed, it does not require third-party involvement.
To answer your first question, I'd say 90mph is probably the most you'd need to use in pretty much all circumstances to safely overtake or maneuver out of a bad situation. If we need to enforce a limit, I'd be erring around that number, personally. The current 155mph limiter that we get in the EU is overkill for road cars outside of Germany, unless there's other places with unrestricted public roads.
I don't recall saying any artificial limit is less safe, I suggested a 65mph limit would be less safe.
I think parents buying a 90mph max car are doing nothing wrong, as that isn't artificially limited to 65mph and would still have the acceleration potential to move out of the way when going the speed limit, albeit slower than some higher spec'd cars would. My first car was a Mazda 2, with no limits on it. It's top speed is 106mph according to Google, and I probably saw 90 once or twice within 4 years of having it.
I'm not sure comparing what we're talking about to tractors is a fair argument - we can drive tractors on the road at 14 in the UK, they don't go on motorways, nor are they the same type of vehicle as a car. I think this goes for a bus as well, it's not only a professional vehicle, with a different class of licence, but they are significantly larger, bright colours, lots of signage stating their restrictions (at least in the UK).
Yes, if the car is only used on the 45/50mph roads then I'd agree 65mph would suffice. If the parent limited to 65, and requested their child didn't go on the highway should we start including GPS limiters as well just incase your kid thought they knew better? It seems like people can't trust their kids anyway in this discussion, as you're wanting to set a limiter on their car, so may as well include some measure to stop them even trying in the first place.
Not particularly sure of your focus on buses here, as I said they're a totally different class of vehicle and clearly don't accelerate the same as personal vehicles for many reasons. Public liability, efficiency, comfort, safety and longevity for starters, and I reckon physics probably comes into play somewhere.
The limiter can be another deterrent, or parental restriction, I just think it's a potentially dangerous one, personally.
Your devil's advocate position was "if you limit the speed for your teen and then need to accelerate to get out of a dangerous situation, what will happen" further clarified as "You should probably start funeral planning anyway if you can’t trust your kid in a vehicle without artificially limiting their speed.".
Had the original limit been 70 mph, I assume you would have said the same thing, as your comment didn't suggest any artificial limit was reasonable.
Hence my devil's advocacy.
> we can drive tractors
While the name comes from farm tractor use some 50 years ago, a Swedish A-tractors is not farm tractor like what you are thinking of. See for examples https://www.curbsideclassic.com/automotive-histories/regiona... and https://www.archivish.com/epas-and-a-tractors-the-slow-swedi... for examples. They can be can be a regular car modified to limit the speed, take out the suspension, shorten the length, and have max two seats. See those links for some images.
> with a different class of licence ...
If you got the same training, does that mean there would be fewer situations where you need to exceed 65 mph on the motorway? Since you asked what could make things safer, it sounds you think additional mandatory training would help.
> should we start including GPS limiters as well just incase your kid thought they knew better?
No clue. That's a far more complicated question which I am ill-informed to answer.
I can make some obvious comments: Exposing the controls for an existing and well-tested speed limiter seems a lot easier than creating an entirely new geofence input system and adding GPS, to say nothing of the more complicated set of failure conditions. The geofence mapper needs to stay up-to-date because road change, so someone has to pay for that service. Most parents who want GPS tracking can already ask their teens to keep their phone on while the car is in use, for viewing aftewards, so the differential safety improvement of a built-in system - if it exists - seems rather low.
But I don't care to defend all conjectural possibilities, only to point out that electronic speed limits for teen drivers is not unreasonable, and already exists for some places, so if it were dangerous we should see that already.
https://www.ford.com/support/how-tos/keys-and-locks/mykey/my...
Excess speed causes a very large proportion of car crashes and traffic jams and injuries.
You asking the question the wrong way:)
Just, we have a lot of different cars today. Some are for comfortable driving, some address the aggressive part of one's personality with capabilities to go very fast. And that: very fast.
Fact is, you can go on any street very fast. If your car allows, you also can conquer that one curve over there with sounding tires.. even the weakest car can be pushed to its limits. The law makers look at the street and decide what's the fastest speed you can go without being to dangerous for yourself and for others. For not having a jungle of different possible speeds for each road, law makers decided to have like three classes of speed 30/40 km/h for inner city - 50/60 km/h for the big streets and 80+130 km/h for the countryside and Autobahn highspeed roads.
So.. should the cars be designed to be slower than speed limit, when speed limit have been chosen deliberately? What's the problem of cars being faster than speed limit, of one's adhere to the limit?
Of course, the measurements of oneself with others in a competitive manner play a role, too. Because the men are like they are, we need rules of which speed limit is one of...
Where I live knives designed primarily for killing humans are illegal to sell, sometimes illegal to own and definitely illegal to carry in public.
That's stuff like commando, flick or spiral bladed knives.
Kitchen, pen or even bush-craft knives generally aren't designed for that but you still can't wave them about in public.
If your analogy holds then are suggesting that if you got caught speeding in a Ferrari or 911 then you'd receive an instant custodial sentence because it was obviously premeditated? That would be the case here if you got into a fight with a spiral knife in your pocket.
Since I'm no car expert (or expert in anything really), I'm eager to hear how wrong my intuition is.
Fundamentally there is limited consumer demand for a governor (but some from parents and also Volvo does it to support their zero deaths goal). In the end, governments should mandate this but the value is not incredibly high compared to many other safety features. Sometimes deadly accidents happen because a driver is going 100mph but for the most part it's people running red lights at 50mph in a 30mph zone (which should be 25mph) that cause the most carnage.
If every car model available for a consumer to purchase has the same advertised speeds, the competition between manufacturers will slowly dry up. I'd guess this would result in less cars being sold.
Would manufacturers compensate by competing in other areas to attract buyers?
Why buy a Kawasaki Ninja H2SX when you could buy a Yamaha N Max...
My ‘89 Mazda 626 had 240km/h, but similar era cars had 320km/h
Despite these usually being a ~2L inline-fours
And given F1 cars have a 1.6L displacement, the relationship between engine size and capability is weak.
The thread is about road cars
Road cars don’t run their engines at 20,000RPM
Displacement is one of the main predictor variables of road cars’ top speeds
You are completely right technically but it’s not an apt comparison given the thread’s topic