Alcohol-Impaired Driving
About 35 t
o 40 percent of traffic fatalities involve alcohol. As part of a broad strategy to improve the performance of commercial drivers, Congress established requirements for a national commercial driver’s license in the Commercial Motor Vehicle Act of 1986. That legislation also proposed reducing the then-prevailing standard for such licenses that defined the offense of driving a commercial vehicle while under the influence of alcohol in terms of blood alcohol concentration (BAC). In most states, the defined limit for alcohol impairment was 0.10 percent BAC at the time the 1986 legislation was enacted; most states have since reduced their limits to 0.08 percent. The Commercial Motor Vehicle Act set a standard of 0.04 percent BAC for commercial drivers and requested a study of alternative standards by the National Academy of Sciences.
Roughly 15 percent of commercial operators involved in fatal crashes had been drinking, according to the best available information in the early 1980s (Special Report 216: Zero Alcohol and Other Options: Limits for Truck and Bus Drivers; TRB 198). Although commercial operators fare better in this regard than the average motorist involved in alcohol-related crashes, there is considerably less tolerance for any alcohol impairment among drivers while working. The victims of crashes involving heavy trucks, regardless of which driver is at fault, are most often the operators of the smaller vehicles.
Performance on driving-related tasks decreases at any BAC above zero, and crash risk increases sharply as BAC rises. Enforcement at low BAC levels is problematic, however, because assessing driver impairment, even with the assistance of breath analysis devices, is more difficult than at higher BAC levels. The majority of the members of the TRB committee addressing this issue recommended that a zero tolerance policy be adopted, with penalties ranging from 30 days’ suspension below 0.04 percent BAC to license revocation for BAC above 0.04. USDOT subsequently adopted a 0.04 percent BAC standard, with a 1-year revocation for offenses at or above that level on the first offense.