All column shift, automatic transmission equipped vehicles 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 added to the ignition switch actuator rod.

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