Over on Transterrestrial, there was a discussion about self driving cars eliminating traffic jams. The site doesn’t allow comments from my computer calling it through a proxy, so I’ll just throw out a few thoughts here.
The discussion focused mostly on cars accelerating from a red light and the amount of time saved when/if they all accelerated together as soon as the light turned green. Some felt that a lot of time would be saved, and some felt that the computer would have to wait for a safe braking distance just as with a human driver with the only savings being a few seconds here and there.
I saw no discussion of timing the lights that some of us do a bit of already. You see a red light in the middle distance and slow enough that it should turn green by the time you get there. So you might be driving 20 mph in a 30 mph zone by the time you reach the now green light. However, you are doing 20 mph through the light when the hurry up and stop drivers are still accelerating from zero. If done right, it is a faster and smoother trip using less fuel and much less wear and tear on the drive train and brakes. By missing this possibility, many people will be in the same position as the composite people that treat their product as black aluminum and fail to get the potential performance gains possible.
With self driving cars it seems likely that the car will know when the light is going to turn green, and if cars coming the other way are likely to do something stupid. It will also be plugged into the local traffic management systems so as to know the speed the lights are timed for. Many places have had their lights set up in such a way as to allow drivers to hit continuous green lights as long as they maintain some exact speed.
With self driving cars interacting with each other there will also have to be early fault detection systems such that cars with problems can be allowed for and given room to recover, pull over, or get out of the way so that the rest can maintain a steady flow. Follow distance with fault detection could be drafting close even at highway speeds.
So my thought is that a mature system of self driving and interacting cars interfaced with traffic control systems will have a flow pattern occasionally glimpsed but seldom maintained. Cars in city traffic will cluster at a speed that allows them to all get through the green light without stopping at all. I timed a light today that had a minute of green. allowing 2 seconds of margin on each end would give 56 seconds of full flow under the control systems I think likely. 56 seconds of cars with a 30 foot spacing center to center at 30 mph would put over 80 cars per lane through one green light, theoretically of course. That is at least 4 times the number I normally see get through per light change.
I think the focus on red lights missed the possibilities of the green lights. I think many of us are going to get blind sided by, not the technology itself, but the way it changes the way we operate. I tend to believe this extends to space far more than we would like to admit.