Do companions of designated drivers drink excessively?

Purpose: A common criticism of designated driver programs (DDPs) is that they promote excessive drinking among companions of the designated driver (DD). Methods: Data were collected from two representative samples of drinkers using computer-assisted telephone interviews (CATIs), and questionnaires administered to customers in barrooms. Results: Most respondents drank moderately—had usual estimated blood alcohol concentrations (BACs) of less than 0.10 when they used DDs. Differences between respondents' estimated BACs when they used a DD and when they drank outside their homes were very small: 0.017 in both samples. Additional analyses examined shifts between lower and higher categories of risk defined as a BAC of less than 0.10 and a BAC of 0.10 or greater. A minority, 15% of CATI and 30% of barroom respondents, switched to the higher risk category when using a DD. These CATI and barroom respondents increased their BACs by an average of 0.089 and 0.11, respectively. Risk associated with this increase was mitigated, however, by respondents' infrequent use of DDs. Implications: Use of DDs was not generally associated with excessive alcohol consumption. Since a minority of respondents did drink heavily when using a DD, programs promoting DD use should caution drinkers that the availability of a DD is not an excuse for excessive consumption, and remind hosts and servers that they should not overserve their guests or customers even when they have a DD.