The speed cycle is designed to move and maneuver at very high speeds. As a result, the bike frame is quite flexible, allowing for shock on somewhat uneven surfaces. It's also able to tilt at exaggerated angles for very quick and dramatic changes in direction. Most importantly, the entire lower body of the driver is encased in a protective cage. Legs are not hanging out to the sides. Thus, there is little risk of injury to the driver when a high speed maneuver goes wrong. It's also nearly impossible for the driver to be thrown from the vehicle. Of course, this also allows most standard 3.5" to 5" figures to ride the cycle, regardless of lower body flexibility.
The Speed Cycle from behind.