Make a game where you have to survive in a traffic jam. Doing this can be on top of cars, in cars, controlling cars, ect. With the main purpose being, a game in a traffic jam.

Take Cluster Truck for example. Use something along those lines.

In this game, you are in a Traffic Jam, running atop trucks. This could be a 2d version, and that can be your Jam. You can also be in a car trying to navigate in a Traffic Jam, Controlling cars in a Traffic Jam, ect. You get the Idea, make me proud :D.