All vehicles equipped with a column-mounted shift lever contain both mechanical and electrical neutral safety start systems. These systems rely on a mechanical block as well as an electrical switch in order to prevent starting the engine in any gear other than PARK or NEUTRAL.

The mechanical block is a wedge-shaped lock bolt that is added to the ignition switch actuator rod.

In either PARK or NEUTRAL, the wedge-shaped lock bolt passes through the slots in the shift bowl and lock bolt allows the lock cylinder to turn and start the engine.