If you plan to incorporate a race management system into your layout, most include software which will control track power at the beginning and end of a race along with track calls. The software typically works in conjunction with a 12 volt relay to turn track power on/off. Using this arrangement, the track power supply remains powered on. The relay is typically wired between the power supply and the driver's stations. When power to the track needs to be turned off, the race management system will cause the relay to "open" which effectively cuts power to the track. To turn power to the track back on, the race management system will cause the relay to "close".
The relay offered below is designed for heavy duty use. This high quality Single Pole Double Throw (SPDT) relay is very reliable; however, it is a good idea to have a spare on hand just in case (particularly if you host race events). Use 1/4" female push-on terminals (do NOT solder them to the relay tabs in case you ever have to remove the wires to replace the relay) to make your wiring connections.