Hacker News Reader

Comment by colordrops | Hacker News Reader

I admit that I'm only doing rough math in my head, but it seems to me that cars bumper to bumper at 100kpm is definitely going to have a greater carrying capacity than intermittent larger vehicles that stop a lot. (Or at least a similar magnitude)

View on HN

I don't expect self-driving cars to drive much more densely than current cars, though, because all or almost all the same reasons we drive with separation still apply for self-driving cars. Where you might think you get some advantages, they will also have disadvantages, too, like being able to compute exactly how risky their behaviors are. People making the cars and writing the car software aren't going to want to stand in court and explain why their car crashed the 50-car dense train because their car software left no possibility of the brakes going out at that exact moment (i.e., no previous sign of brake failure), and caused a huge crash because none of the cars had any buffer for failure.

Personally I expect self-driving cars to drive a great deal more conservatively than humans as a result, and I think self-driving cars are going to end up demanding a lot more space and buffer on the freeways. And if they don't at first, one day you'll way up and they suddenly all will, because somebody won some lawsuit and a software update was pushed overnight to double the buffers.

The fundamental difference between human and automated drivers is that humans aren't going to get any better. Software based systems will get to human level then continue to improve to the limits of computing and physics, which is certainly better than humans.

And we haven't even considered networking. When the cars are all talking to each and routed together then it's fundamentally a single machine.

The laws and systems will evolve with capabilities rather than getting stuck on supporting the earliest generation of self driving vehicles and norms.

I tend to agree, I expect that as a practical matter autonomous cars will be conservatively driven, e.g. with large buffer zones, gentle acceleration, safety-above-all-else.

I think other drivers will adapt to this and start taking advantage. Think of what happens when you leave a legal following distance in front of you now, in traffic. Now imagine an autonomous car in the same situation. It would probably end up stopped.

I'm not sure this is a bad thing. Often times, traffic jams are caused by not enough spacing, or unobservant drivers resulting in sudden breaking, and a knock-on effect. Would need to simulate to confirm, but I suspect that more vehicles giving enough stopping distance, and accelerating smoothly would improve traffic flow, even with the addition of more defector (defective?) drivers.

Might as well imagine autonomous-only lanes while we're speculating.

The primary reason we drive with separation is our reaction time. Computers can react must faster. In addition they can actually talk to the cars around them. They could literally form a train. We won't switch to self driving cars until they can drive better than humans. If they have to leave a larger buffer, then the work isn't done.

I don't think it applies that easily.

There's still a chance an automated car encounters something that couldn't be spotted / reacted to. For example a deer/kangaroo/whatever jumping right in front of it. If the cars keep their distance, only the first one crashes. If they form a minimum-spacing train, the only message they can send to the following ones is "you're screwed now".

A deer would be unlikely to jump into a train of cars. They usually get caught by cars that have space in front of them. I know you are just giving a single example, but anything that applies to an actual train would apply to a virtual train as well. I don't understand why not having a physical latch between cars makes any real difference.

A deer doesn't affect a real train that much due to the mass difference. In case of cars though they cause serious damage. If the following cars don't keep a distance they end up immediately crashing into the first one, multiplying the damage.

I don't have much experience with deer behaviour, but kangaroos will happily jump right into anything moving. They will even hit the side of your car sometimes (which they should've obviously seen coming)

The major reason we drive with the space between cars that we do is human reaction time. That is at least an order of magnitude better in autonomous cars.

Cars driving bumper-to-bumper at 100km/h would be extraordinarily unsafe.

Reply on news.ycombinator.com