Comment by bluGill
7 days ago
Doesn't really matter - in the real world everybody is tailgating. Drivers need to maintain 3 seconds (GP was using 2 seconds which safety experts have not declared too little) between cars for safety reasons. However drivers are instead maintaining more like .5 seconds between cars. As such nearly every city needs about 5 times as many lanes as they currently have when people finally start demanding "just one more lane"! 5 times - that puts Huston level freeways in Des Moines.
If you maintain the proper following distance at maximum capacity when there is an issue you can momentarily drop to 1 second (while braking) and then expand back to normal and there is no effect on traffic.
I'm going to double-down on this point because it does matter. In the real world some people are tailgating, but that does not cause traffic jams if and only if the road is running below peak capacity, where negative feedback self-corrects those traffic density deviations and gradually smooths everything back out. (Unless the tailgater causes a crash, of course).
But if the average following distance is such that the road is exactly at the peak of throughput, or any smaller, then any momentary dip into tighter following distances pushes the road it into a positive feedback operating mode, which triggers a traffic jam.
If you haven't seen it, here is a classic experiment demonstrating the effect: https://www.youtube.com/watch?v=Suugn-p5C1M
(But obviously the solution to traffic isn't 5 more lanes, it's viable alternatives to driving!)