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Comment by mschy | Hacker News Reader

In practice what it means is that if you're about to crash into something, and you hit the brakes, that it hits them 100% right off the bat, instead of the 50% or 80% that most people would go for.

I've not used the system in the Prius, but I've used a competing system and it's not at all surprising.

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In many cases you're better off trying to steer around the collision than (or in addition to) stopping short of it. I've seen a few crashes where people could have just steered onto the shoulder or median to avoid the crash but it seems that they just applied the brakes and hoped for the best.

I don't think driver's education in the USA teaches emergency maneuvering much. How is it elsewhere?

Nothing taught in Australia, at least conventionally. My driving instructor was a retired police driver trainer, I benefited greatly from his experience and understanding of vehicles. Never had an accident, but avoided several via quick thinking + knowledge of how the car will react and what options I have when driving.

For what it's worth, that's the main focus of the Motorcycle Safety Foundation course. If I remember correctly, 35 mph is the speed at which is easier/faster/safer to swerve than to try to stop a two-wheeled vehicle.

My drivers education course (in the US) emphasized steering to avoid a collision first, and then braking afterwards. We were taught that colliding with a pole at 35 mph is better than doing so with oncoming traffic for a total effect of 70 mph. It also reduces the chances of injury.

After reading that pilots are the safest drivers, I've made sure to always look around my car as I drive.

Ditto. The thing that seemed to trip up most people in the simulators was remembering to correct for the swerve. Most would turn hard right/left to avoid the obstacle and then forget to make a fast counter-turn to avoid running off the road.

Remember that F = ma.

Hitting another car of the same size coming from the opposite side when each car is doing 35 mph is pretty similar to hitting a concrete wall at 35 mph. There is no 70 mph effect. The reason the pole would be safer is that it has some give. Lower acceleration = lower force.

If someone could explain why I was voted down, that would be great. Thanks.

I didn't vote you down, but you cannot assume the cars are of identical size and mass, or indeed that it's a car at all. Hit a truck at 35, while he is also doing 35, and you'll feel a 70mph effect all right. For a few milliseconds.

Unfortunately, poles, especially old ones, do not have as much give as one would like, and large trees have basically none. Plus, their narrow aspect is a very bad thing to hit; cars are designed to collide with large, flat, wide objects and to crumple accordingly to wash off energy. Hitting an immoveable narrow object is outside this design consideration and cars have a nasty tendency to wrap around it.

I was just making the point that justifying swerving out due to some undefined 70 mph effect is incorrect if you don't know what you're dealing with. And that whoever came up this 70 vs. 35 mph effect justification should realise that it mostly applies to e.g. the truck example you gave and somewhat to cars of significantly different mass / size. Therefore it's confusing advice and obscures other possible good reasons for swerving out.

I believe these systems don't have the effect until the point at which steering is no longer the option. The idea isn't so much to avoid the accident, but rather to try to bleed as much of the force of the accident out through braking as possible.

If you can get the brakes fully engaged you can reduce the severity of an accident pretty substantially, even if you can't fully avoid it.

It's not taught in South Africa, although we have a number of Advanced Driving Courses which teaches you anything from skid control to collision avoidance.

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