i think i remember road rash was that the one where you drove in different competitions to win prizes and you could push and punch everyone off their bikes but you had to be carful u wernt slow because the police would catch u that was so cool.
in responce to your question y not us mat edit and use a road texture like in the candy land demo? then set the dirt texture to one and use there texture collision thingy to make your bike slow down on it.

cant wait to see this game and i hopes it lives up to the origanal.
Darkworlds are all around us
most of us are still half asleep
Current project : Creature tournament