This paper presents an overview of the theory and implementation of a touch-based optical sensor for monitoring the alcohol concentration in the driver of a vehicle. This novel sensor is intended to improve driver safety by providing a non-intrusive means of notifying a driver when their blood alcohol concentration may be too high to operate a vehicle safely. The optical alcohol detection system has successfully completed several stages of development and validation. A commercially available, industrial version of the system (Mark 1) has undergone extensive clinical testing and field validation. Under the DADSS (Driver Alcohol Detection System for Safety) Program, a compact semiconductor version (Mark 2) of the optical system has been developed targeting use in consumer vehicles. Based on proven semiconductor laser technologies, the Mark 2 sensor system has demonstrated excellent spectral accuracy and precision and is currently undergoing laboratory validation testing. A demonstration vehicle version of the system has been designed and will be implemented following completion of the laboratory validation testing.