A multiply-redundant system that prevents a driver from starting and/or moving a vehicle if a compressed natural gas fill system is not correctly and completely disconnected from the vehicle. One or more sensors in combination with one or more optional microswitches combine to lock-out the vehicle's ignition or otherwise prevent it from starting and/or moving. For different levels of safety, different combinations of sensors can be used with the lowest level having a single proximity sensor sensing the presence or absence of a high-pressure fill hose. The highest level of safety being achieved by having separate proximity sensors on the fuel fill hose fitting, the gas cap cover and a manual safety valve along with a redundant microswitch. An optional override that may be restricted as to the number of times it can be used can allow starting with a faulty sensor in order to allow maintenance.

A method to prevent intoxicated operation is described. The method includes providing instructions to a vehicle user to position a vehicle user body portion posture in a predefined alignment. The method further includes obtaining the vehicle user body portion posture from a first vehicle detector, and determining whether the vehicle user body portion posture is in the predefined alignment. The method includes activating a plurality of vehicle visual indicators to illuminate in a predefined manner when the vehicle user body portion posture is in the predefined alignment. The method further includes providing instructions to the vehicle user to move vehicle user eyes to track the plurality of vehicle visual indicators, and obtaining a vehicle user eye movement from a second vehicle detector. The method further includes determining whether the vehicle user eye movement meets a predetermined condition, and actuating a control action accordingly.

A multiply-redundant system that prevents a driver from starting and/or moving a vehicle if a compressed natural gas fill system is not correctly and completely disconnected from the vehicle. One or more sensors in combination with one or more optional microswitches combine to lock-out the vehicle's ignition or otherwise prevent it from starting and/or moving. For different levels of safety, different combinations of sensors can be used with the lowest level having a single proximity sensor sensing the presence or absence of a high-pressure fill hose. The highest level of safety being achieved by having separate proximity sensors on the fuel fill hose fitting, the gas cap cover and a manual safety valve along with a redundant microswitch. An optional override that may be restricted as to the number of times it can be used can allow starting with a faulty sensor in order to allow maintenance.