Races (known as heats) consist of four riders racing over four laps from a standing start. Riders wear different coloured helmets, traditionally in team events red and blue denote home team riders, and white and yellow/black quartered colours (latterly plain yellow) denote visiting riders. The starting area is divided into a grid of four equal parts and the riders from each team must take their place in alternate grids or "gates". The colours also denote starting positions in individual events; Red is the inside gate (gate 1), blue starts from gate 2, white starts from gate 3 and yellow/black starts on the outside (gate 4). Riders must be able to get their bikes to the start line under their own power, without any external assistance and not by pushing the machine, then line up in parallel.