The Nerf Bar or Sidebars originally designed for the Gemini XR-1 Caged Racing Go Kart(Champ Karts) are retrofitted for racing lawnmowers. 

The Nerf Bars add protection to the driver on the sides in cases where the driver spins and can be struck perpendicular by another kart. It can also prevent the side of open wheels from getting tangled from the tight side by side racing.