My first year in grad school I had a class in nonlinear wave propagation, which happens to be used to model traffic flow. It significantly influenced my thinking in congested traffic, when merging lanes, etc.
One thing we learned was that traffic flows smoother and will be able to pull away from a red light faster if there is space between cars. I forget the optimum number, but it was about 8-10' or so, which might be enough to see the rear tires or back bumper.
Anyhow, the idea is that when the light turns red, if there is sufficient space between the cars, they can all begin accelerating and moving together. When cars are bunched up, they start moving one at a time, front to back, as if a "wave" rolls back through the lane.
Years later I bumped into a VDOT engineer at a picnic, and we got talking about that, and his eyes lit up. He had no background in the theory, but he knew the practical side of traffic studies and planning, and he said it was exactly true. Worst thing cars can do is bunch up at a light. Any increase in the density of cars in the lane is offset and then some by the fact that the cars begin accelerating one at a time, from a standstill. So if you're the tenth car back, for example, you have to wait for 1 to move, then 2 to react and move, then 3, then 4, etc... until car 9 moves, and then you react and move. That's a bunch of delays. With good spacing between cars, you can all start rolling more or less at the same time, and more cars will make it through the light.
This is pretty easy to test in practice, though getting a whole line of cars to try it is probably impossible. But if you're ever #2 in line at a red light, keep about 8-10' of space, and when the light turns red, you can begin moving at the exact same time/speed/acceleration as car #1.
