Fastest Actual Speed of an RC: If you clocked a hobby-grade RC vehicle at top speed using a police radar gun, you'd probably get a speed anywhere between 10 to 70 mph. Some dragsters and specially modified RCs can top speeds in excess of 100 mph but that's the exception and not the norm.
Actual Speed and Size of an RC: There is a loose relationship between the size or scale of the RC vehicle and its actual speed. A 1:10 scale RC would go about 1/10 the speed of the full scale vehicle it's modeled after. This doesn't always hold true. RC toys, especially those for toddlers and pre-schoolers are much slower. Some modified RC vehicles may have actual speeds that are much faster than you might expect for their scale size.

