The 2021 Bipartisan Infrastructure Law included provisions directing the National Highway Traffic Safety Administration (NHTSA) to promulgate rules to require automakers to equip new vehicles with impaired driving detectors.  The rulemaking process will likely take years as the agency investigates currently available technology and technology currently under development.  

The dominant technology currently is the ignition interlock device.  That is a device which requires the driver to provide a breath sample which is tested for the presence of ethyl alcohol.  A positive result over the margin of error can result in the vehicle either not starting or notice that the vehicle will be stopping followed by stopping.  This is an active detector since it requires action by the operator of the vehicle.  It has many limitations.  It cannot detect substances other than alcohol.  It cannot detect fatigued or otherwise impaired driving.  The 2021 law makes it clear that this is not the type of detector that will be mandated.

Some new vehicles are already equipped with passive detectors which can trigger audio and visual alerts if it detects the driver having difficulty maintaining the lane of travel.  It is these types of detectors that the rulemaking  One type of passive detector could be a device which samples the cabin air for the presence of alcohol, but that likely would not be specific enough, since it could detect alcohol in the exhalations of passengers in the vehicle instead of the driver.  Obviously, the technology would not want to prevent a taxi driver or designated driver from transporting inebriated passengers home.  These and other issues will have to be explored by NHTSA before any new rule can be promulgated which will then set a phase-in period for implementation of the rule.