If *I* had made it...
The multiplier thing flew over my head, I think: didn't you say you get more time if you send five of the same colored cars in one direction? See, I figured you could continue to get that time bonus if you sent, say, ten cars, or fifteen cars of the same color. Maybe I didn't understand. Anyway, this game BEGS for a variety of speeds. I realize that there's such a thing as a "speed limit" and that, realistically, people slow to a crawl when someone is directing traffic, but if you set this game in, say, POST-APOCALYPSE LOS ANGELES (or modern day Los Angeles: you'd probably get the same effect *drum solo*) and added a variety of cars that travel at different speeds, OR if you had a certain kind of car accelerate up to the cop, but then drive away slowly and another type drive up to the cop slowly and accelerate off in a hurry (my strategy) and you added the element of having to avoid accidents by directing the different speeds of cars into different lanes (and also added a few lanes)...
If I was going to make a game like this, I think I'd probably explore all of that. As it stands, though, it didn't last very long and wasn't worth a second playthrough.