Gravity only — vehicles must coast downhill; Initial push at start permitted (typically 3-second team push from start gate); No engines, motors, pedaling, paddles, or stored energy (batteries, springs, etc.)
Why people argue about this
People often assume that since it's called "Permitted Propulsion," they can use some form of propulsion other than gravity for their race starts or descents, but in fact, the official rule clearly states only gravity is allowed during these phases, no engines, motors, pedaling, or stored energy.
