Nice game! I like the music, and controlling the flow of traffic and trying to make it as efficient as possible is fun. I think it might add to the fun if there were more ways to manipulate traffic, like adding stop signs and lights and what-not. You could also add to the challenge of trying to prevent jams by adding different types of vehicles that vary in size, speed and/or durability.
Having cars be able to move through houses and bill boards was a bit confusing.
There was an odd occurrence where I would randomly get 100 or 200 cash for no apparent reason. I'm not sure if this is a bug or just a feature that I was unaware of. Also, for some reason I couldn't click the buttons in the pause menu (might have something to do with playing it in a browser, but I don't know).
The art style is a bit lacking. It would look a lot better if the road lines (and vehicles) always pointed in the direction of the flow of traffic, rather than always facing to the right.
Good job!