Ok, I have started to do game like this for my brother because he enjoys games like that and I have done now accelerating and deceleration, also turning. It would be nice if someone would tell these things:
1. How you do like that it would count when you count one lap and you couldn't cheat like just going it again and again the finish line.
2. How you make the cars to "slide" when you turn...
3. How about skitching marks (when decelerating??)
1. One way to do this is to work out the distance the player has gone, by adding the car's current speed to a counter every 1/50th of a second. Then make sure that when they collide with the start/finish line that the distance they have travelled is greater than a minimum value which you set, and then set their distance back to zero.