This is really well done. Would make a solid mobile game since it's pretty much touch compatible already.
Only "issue" is that sometimes you have to wait for quite a while for a situation that actually requires you to stop any cars. A lot of the time you can just let the cars go straight through no problem.
Rather than an endless game, I could see a level based approach work well for this, with different kinds of intersections, maybe even multiple intersections (Though The endless mode is still good).