I developed some kind of idea for this;
1. As long as you're on the road, the score increases.
2. Dodge oncoming traffic; this forces you to get off the road (for a moment)
3. Game ends when you hit oncoming traffic or trees
So this is some kind of first draft, the idea will probably evolve into something more exciting

The oncoming traffic is already added, try it! (might need to clear cache) Still no collision, I first need to come up with something that makes the other traffic follow the road and something that prevents traffic crashing into each other.