I like the concept. Love how the cars flip over when they collide.
I feel like the arrow key controls are a little confusing since it's an isometric perspective. I feel like toggling the lights by clicking on them would work better, and it'd even work as a mobile game that way.
You could also add some additional feedback on which direction the traffic is able to move by adding an arrow along the ground when the light is toggled. As it is, the lights are pretty small so I found myself losing track of which lights I had toggled.