I don’t think I would do this with physics to be honest, too unpredictable with different maps, like you said it might shoot off a ramp or something.
I would just create a regular static mesh and it’s always got a fixed speed anyways just give it it’s starting speed and direction and fire it off. Set it’s Z position and rotation to offset from the road below and to take the angle of the road (you can do this with 2 line traces, 1 directly down and 1 at an angle in front, use trigonometry to calculate the angle it should be to match) and do a basic reflection off the wall in pretty much the same way.