Validity of the passive alcohol sensor for estimating BACs in DWI-enforcement operations

The effectiveness of driving while intoxicated (DWI) operations in deterring impaired driving depends on the ability of police officers to detect heavy drinkers. The passive alcohol sensor (PAS), which can detect alcohol in expired breath at a distance of 6 inches from the face, provides a means for detecting heavy drinking within 15-30 seconds. The objective of this study was to determine the accuracy of the PAS unit for estimating the blood alcohol concentration (BAC) of drivers and study its potential use as a screening device for estimating BAC in relation to several factors related to its use (age, gender, light conditions, and police confidence in the PAS measure).

A recent study funded by the National Highway Traffic Safety Administration of the BAC levels of crash-involved and randomly stopped drivers as a control group for comparison provided 12,587 cases in which both a breath test and a PAS measure of BAC were obtained for each driver studied. This research involved a secondary analysis of that data set using regression and receiver operator curves methodology to determine the accuracy and utility of the PA S for use as a screening device for DWI violations.

PAS scores were a strong predictor of a driver's BAC status. The only other variable having a significant and consistent relationship independent of PA S was police confidence. Detection sensitivity and specificity for each PA S cut-point score were estimated.

By selecting a PAS cut-point score appropriate to the enforcement operation being undertaken, the PA S can be an effective tool for officers when deciding whether to initiate a DWI investigation.