The Automotive Coalition for Traffic Safety (ACTS) and the National Highway Traffic Safety Administration (NHTSA) have commenced a five-year cooperative agreement exploring the feasibility of, and the public policy challenges associated with, widespread use of in-vehicle alcohol detection technology to prevent alcohol-impaired driving. This effort, known as the Driver Alcohol Detection System for Safety (DADSS) program, aims to develop technologies that could be a component of a system to prevent the vehicle from being driven when the device registers that the driver's blood alcohol concentration (BAC) exceeds the legal limit (currently 0.08 g/dL throughout the United States). For DADSS installation as original equipment in new vehicles there are critical requirements to be met. Alcohol detection technology must be seamless to the driver and be able to quickly and accurately measure the driver's BAC non-invasively. DADSS devices must be compatible for mass-production at a moderate price, be durable, meet high levels of reliability, and require little or no maintenance. Potential technological approaches have been identified and thorough analyses undertaken to determine candidates for further development, utilizing a clear understanding of the processes by which alcohol is absorbed into the blood stream, distributed within the body, and eliminated from it. This paper describes what is known regarding alcohol measurement via various methods, and details which technologies deserve further study. Two approaches are identified that have considerable promise in measuring driver BAC non-invasively within the time and accuracy constraints: 1) Tissue Spectrometry, a touch-based approach allowing estimation of alcohol in tissue through detection of light absorption at a particular wavelength from a beam of near-infrared light reflected from within the subject's tissue, 2) Distant Spectrometry using part of the infrared light spectrum where the light is transmitted toward the subject from a source that receives and analyses the reflected and absorbed spectrum, thereby allowing assessment of alcohol concentration in the subject's exhaled breath.