THERE IS NO SUCH THING AS SCALE SPEED.

A RC car is a small vehicle in a normal sized world. Speed is distance over time and an RC car traveling at 20mph is just that. If you made the car bigger, it would still be traveling at 20 mph, because the world (and our concept of time) are a constant.

Forces Related to a crash are solely the forces you would expect from an object of that size and weight traveling at that speed.