Tracks alone won't be enough, you'll need also a physics module.
Tracks require two things, a modification to the road system (for track foundation), and a spline-based geometry generator (repeater, for cross ties and rails).
Repeater requires a modification of the material system to support small instanced geometry rendering without a full blown object pipeline. It's going to be used also for other road and railroad related things like poles, guard rails, but also highway connections, bridges and tunnels.
Material system update depends on shader system update (which is now mostly ready, so it's waiting on a free time slot).
