How do you make a toy car roll?

Here's a step-by-step video:YouTube.com/watch?v=LSzr4zX_RG8">http://www.YouTube.com/watch?v=LSzr4zX_RG8

And some more instructions:

http://books.google.com/books?id=_8So0iUej7EC&pg=PA43&lpg=PA43&dq=rubber+band+roll+back+toy&source=web&ots=OAeI0Hewos&sig=oNZX4wqt-75v_LwfohMRKtwSM7A&hl=en&sa=X&oi=book_result&resnum=2&ct=result#PPA45,M1