Kick Scooter riders use a lot of energy overcoming inertia when kicking off.
This scooter has a spring under the deck which stores the energy usually lost in braking by loading the spring when you let out a rear wheel clutch. When you start up the spring helps drive the rear wheel to make your takeoff easier.
You could use the deck itself as the spring but you would have to have the gearing very high, or you would end up standing on a tall humped deck.
This could also be done with a compressor and an air tank, but the spring seems simpler.-- macrumpton, May 14 2004random, halfbakery