Most truck and tractor cabs are equipped with heating, ventilation, and air-conditioning systems, usually known as HVAC. A typical truck has an HVAC or climate control system used to condition the air in the driver cab and the sleeper unit if so equipped. Many current trucks complement climate control systems with auxiliary systems that automatically maintain a comfortable cab and/or engine temperature with engine shutdown.
Because many jurisdictions enforce anti-idling legislation, auxiliary climate control systems are becoming more common. Such systems allow a driver to sleep without the need to keep the engine running.