mini project related to sense pits on the way of car

[iiitd&m boy]

can anyonehelp me to make a small car which can sense and count small Pits which comes on its way, i have already made a car but no idea,which sensor can i use to sense pits.......(can think of small pits on roads)
the size of pit will be very small and iam using two 100rpm motor,do i need to synchronize this two motors?
any idea is helpfull..........

 

[nandhu015]

You can use distance sensor, It may be either ultrasonic or ir.