Simple Newton's Laws at work. I wouldn't do it very far into a car lane. On a shoulder, no problem. Even better is if the road edge has a good slope off that helps gain momentum with a sharp right swerve. It must be how they rode 3 speeds in olde England. My SA 5 only goes down to low 40's.

Now try to expalin how waggling changes the forces in the path a cranks propultion, also involving the arms. ha