WRANGLER uses a traditional ladder frame chassis, the preferred off-road method of construction but one not favoured by road safety experts. Dual airbags are standard and anti-lock brakes are not available. A skid plate protects the fuel tank while a heavy-duty steel bar cage provides roll-over protection in all models. The soft-top has half doors that have seen front seat occupants lean out of the vehicle during crash tests. The brake-park interlock on models with auto transmission will not allow the shifter to be taken out of park until the brake pedal is depressed. A clutch-starter interlock on manual transmission Wranglers will not start the engine until the clutch pedal is depressed.