S.O.S. Mathematics CyberBoard

I'm having a lot of trouble figuring out this problem.

How should red/green traffic lights be timed in a city where the street map is a grid? First assume that each street is equally traveled by cars and have the same speed limit. What happens if the speed limits for east/west streets are different that the speed limits for south/north streets? What if some streets are more heavily used than others?

So far I've only been able to make assumptions to attempt the problem, but still unable to figure it out. I've been trying to do the first one where each street is equally travelled and they have the same speed

I'm going to assume that the cars can only travel in the direction they're going (meaning they only travel in one direction and do not make any turns). This implies that at any given intersection, cars are moving and cars are stopped (Red/Green). So we can think of any intersection as a binary. We obviously want to minimize the time waited among all the cars. The problem I have now is how to relate the intersections to each other and find a general formula for the waiting time. I've read online about the genetic algorithm, ant colony algorithm, etc. and is that the only possible way to do this problem? I feel like my problem is a more simplified version and should be easier. Any input would be great. Thanks