[sp332]

This sounds like an argument for introducing a separate class of "city car" to the USA. On a highway, I want a big comfy car that can be efficient at 55-65 MPH, and protect me in a collision at those speeds. In a city, I don't really need that.

[graylights]

That big comfy car that protects you from highway collisions accomplishes that by shifting the impact toward the smaller car. It doesn't increase overall highway safety, just steals it from others in your favor.

[kahirsch]

Large cars are also safer in single-vehicle collisions, which account for 65% of traffic deaths. There is some adverse effect on occupants of other vehicles, but this is much smaller than the advantage in safety from the large vehicle.

It is definitely not true that it "just steals it from others".

[SixSigma]

It definitely is true. In a collision the vehicles absorb the energy of the collision inversely proportional to their relative masses i.e. the lighter car takes the brunt of the crash.

Safety researchers are responding by using active protection systems: in vehicles equippped with v2v transcievers will stiffen or soften their crash protection systems based upon the relative masses of the vehicles.

[thaumasiotes]

Imagine the following:

- two people driving paper-thin cars crash into each other head-on at 60 mph. The cars divide the energy of the collision evenly, disintegrate, and pass on a lot of energy to their passengers.

- two people driving huge voluminous and massive SUVs crash into each other head-on at 60 mph. The SUVs divide the energy of the collision evenly, warping into unrecognizable crumply wads of steel. The passengers take less damage than in the earlier scenario.

This is impossible?

[SixSigma]

Sounds like you're restating my premise.

[thaumasiotes]

Yes, the question mark indicates that I want you to confirm I'm understanding correctly. Seems so. Why is that impossible? We know from the trivial case of a person flying along at 60 mph with no car (maybe they were fired out of a cannon?) that you can reduce damage to the passenger by adding mass.

[Dylan16807]

You're ignoring the word 'just'.

[malandrew]

Of that 65% that is single vehicle collisions, what causes are responsible for most of those and where do most of those collisions take place? suburbs, rural, city?

I would imagine that the overwhelming majority of single vehicle collisions are in low density suburbs.

I would also imagine that the overwhelming majority of those deaths involved colliding with a stationary, immovable object, such as a tree or traffic pole. In such a case, smaller vehicles will much less kinetic energy, but still as much thought given to their safety designs, should be much safer.

[Dylan16807]

Big doesn't have to mean particularly heavy, and it's ridiculous of you to suggest that a couple extra feet of crumple zone isn't going to make impacts less forceful.

[Gracana]

What about all the safety features found in larger cars? What about single-vehicle accidents? I don't need to drive a logging truck to feel safe, but I'd much rather drive a new corolla than an 80s model. Solid pillars and increased crumple zones and multiple airbags make a car bulkier, but the safety improvement is much greater than a simple function of weight.

[collyw]

I would feel far safer on my bike being hit by one of these larger cars and their safety features.

[mikeash]

I don't think that's true. Consider the two extremes.

1. You somehow manage to get a cardboard box up to 70MPH. You strike another fellow pulling the same trick. How badly are the two of you hurt? I believe the chances are excellent that you both die immediately.

2. You somehow manage to get a container ship up to 70MPH. You strike another fellow pulling the same trick. How badly are you hurt? If you're strapped in and not near the front, I believe chances are excellent that you'll both walk (swim) away.

[seanmcdirmid]

Sounds like a tuktuk, many cities in Asia have them, but they mix with car traffic.