A Kill switch
is equipment designed to disconnect
all electric power
. Most sanctioning bodies
require that a kill switch be installed in every race car
before it is allowed to compete.
The reason is safety. Most ancilliary equipment on a road racing car is powered by electricity in order to limit the drain on engine power. This includes the fuel pumps. In a race car, the fuel pumps are manually switched, and do not shut off with the engine. During a serious incident it can be desirable to kill all power to keep the fuel in the car's fuel cell rather than leaking it all over the pavement, hot engine, or driver. Let me give an example. in 1999 a Riley & Scott --Ford pulled off on the back straight during an IMSA race at Mid Ohio Sports Car Course. A rail had broken in the fuel injection system, and raw fuel was shooting out on the engine, which promptly ignited. That set the car on fire. The driver pulled the car off the track and exited the car as quickly as possible, without turning off the pumps. So the fuel pumps continued to operate, feeding fuel into the conflagration.. A $200K race car burned to the ground. For that reason corner workers routinely use the switch to kill the power of disabled race cars.
Kill switches are required to be readily accessable from outside the car. Often kill switches are located at the very front of where the driver or passenger window.. Some have a removable key which must be put back in place before the switch will flow electricity.