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Comment by Strongerpass | Hacker News Reader

I agree in general but I think "A car traveling 30 mph is absolutely as lethal as a car traveling 10 mph faster than that." is a bit weak.

The speed of cars matter, obviously. If you are hit by a car driving 50km/h you will die 8 out of 10 times. If the car is only driving in 30 km/h you will only die 1 out of the 10 times. In other words, it's not a linear scale and the idea that you can drive a bit faster without making yourself substantially more dangerous is incorrect.

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You might be factually correct, but you are misunderstanding the point of the parent poster. What makewavesnotwar is saying is simply that making exaggerated arguments for this technology in the name of making us safer is not a sufficient reason to introduce the technology. Perhaps if they had used larger numbers like 50 MPH relative to 60MPH that point would have been made clearer.

I understood the point well and I agreed with the poster. But in my view, if you are going to argue that we don't need more automated monitoring in traffic then claiming that speed has little impact on fatalities seems quite weird.

As a pedestrian and cycling advocate, more regulation of cars seems like a good idea for me. That said, the analogy is just that, an analogy so I don't think it's fair to nitpick it.

> A car traveling 30 mph is absolutely as lethal as a car traveling 10 mph faster than that.

What was this an analogy for? I missed it.

As in makewavesnotwar point about surveillance of the general population and not just immigrants.

Plus your chance of being hit at all is much lower at 30km/h because the driver has more time to react.

if you're on a highway, then a car driving 30mph is much more dangerous than one which is 10mph over speed limit.

That's kind of moot, at least where I live. Less than 3% of deaths were caused by this so its not really significant. Pedestrians killed were many times higher for example.

It really depends. In the US pedestrians account ~10% of total number of traffic related deaths.

Do you have a statistic confirming that? Most highway deaths are due to speed, not due to driving slow. Driving slow can provoke people behind to do dangerous things, but it's on them, not on a slow driver.

Maybe most accidents are due to speed because a lot fewer people drive too slowly.

Actually the real problem is differential in speed.

So a car going 80 in a 60 hitting a car going 30 in a 60 is worse than a car going 80 in a 60 hitting a car going 60.

Now I'd rather everyone stay within a narrow limit and not go over the 'limit'.

Differential kills.

Do you have any support for this argument at all? It seems to overlook the reality of the situation. When one car is in a collision with another, regardless of their relative velocities, when they collide, in a serious accident they will both rapidly decelerate to a speed of zero. That's what the danger is. Their absolute speed has dangers above and beyond their relative velocities -- less control of the vehicle and greater kinetic energy wrt the environment.So, a car traveling at 25 hitting a car moving at 5 may have a 20 kph/mph differential, but the danger is minimal compared to a car traveling at 95 hitting a car at 85, where both vehicles quickly go down to zero, rolling and smashing into barriers and other vehicles along the way.

Right - a head-on collision between objects of equal mass and velocity is equivalent to one hitting a brick wall (or immovable object) - it loses all its kinetic energy on the spot, turning it into heat and mechanical work (e.g. crushing the car and driver). Objects of slightly different mass or velocity means the work done on each is shifted, the heavier or faster one 'winning' a bit but still. The absolute values of the velocities are hugely important.

Agreed regarding absolute value, my usage of differential is not comparing different scenarios but focused on one.

So 25 mph + 40 mph in a 25 mph is dangerous.

80 mph + 55 mph in a 55 mph is dangerous.

Obviously the former has much less energy, but within itself, the differential is what creates the most accidents and danger.

I'm not saying that differential is all that matters. A car doing zero and one doing 20 in an accident is much better than the 80 vs. 70 example.

What I'm saying is apples to apples.

Speed limit is 60, car doing 50 + car doing 80 is a lot more dangerous than two cars doing 60. In both an accident and in actually causing one to begin with.

I agree with most of what you're saying.

Prime example

Quebec woman who stopped on highway for ducks, causing fatal crash, loses appeal

Of course on a web-site for nerds, commentaters are going to focus on an irrelevant technical detail and miss the larger point.

I don't see how it's an irrelevant detail. If enforcing the speed limit does indeed save lives then I'm more inclined to accept some loss of privacy.

Of course on a web site for nerds, commentators are going to claim that a massive loss of life due to what they consider to be some irrelevant factor is just a technical detail which can be ignored.

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