Frustrating
I like the idea you were going for, but the vehicle creation is flawed and frustrating. Vehicles that look like they're attached come apart when put on the track, and there's no way to really gauge whether it'll work until it doesn't. Also, some type of control on the speed would be helpful. Try to bring in elements from games that are all about maneuvering over obstacles where left and right are accelerate and brake and up and down are for tilt (perhaps, in the case of a vehicle, shiftable shock controls).
Overall, a good attempt, but it needs more polish.