Newswise — Regular statewide retail checks for compliance with the legal drinking age are associated with a sustained reduction in alcohol-related crashes for drivers aged under 21, according to an analysis of 11 years’ data from South Carolina. Previous research has shown that reductions in underage drinking lead to a decrease in drink-driving and alcohol-related crashes. However, few studies have assessed the impact of purposeful alcohol compliance checks – in which authorities use an underage informant to attempt to buy alcohol – on drink-related road accidents. The new study, reported in Alcoholism: Clinical and Experimental Research, evaluated the impact of the South Carolina Alcohol Enforcement Team (AET) program for reducing retail alcohol access to underage youth on drinking and driving crashes among drivers under 21 years old.

The researchers analyzed compliance check and traffic crash records from 2006 (just before the AET program expanded statewide in 2007) through 2016. County compliance check data were used to calculate the percentage of the under-21 state population exposed to compliance checks in a given month. The research team then examined the relationship over time between compliance check exposure and drink-related crashes involving drivers aged under 21 and used statistical modeling to estimate the impact of the AET program. Drink-driving crashes among drivers aged 21+ were also assessed, to control for other factors (besides underage compliance checks) that may influence alcohol-involved traffic crashes.

Across the state, almost 65,000 compliance checks were conducted over the 126-month study period (averaging >500 a month), of which almost 9,000 resulted in an illegal alcohol purchase. Youth exposure to compliance checks varied over time – rising through mid-2008 after the statewide program expansion, before declining through to 2010 following a reduction in enforcement funding, and then increasing and stabilizing through 2016 after a subsequent policy shift. The latter stable period (2011-2016) marked a 7-fold increase in statewide compliance check exposure compared to the pre-AET period. By 2016-end, 80% of the underage South Carolina population was exposed to regular compliance checks. The proportion of compliance checks that resulted in an alcohol purchase declined as checks increased, rose as checks declined, and declined again and stabilized as checks intensified from 2010. Through to the end of 2016, only around 9% of compliance checks involved a successful alcohol purchase.

In total over the study period, there were 4,782 road crashes in which under 21-year-old drivers were assessed by law enforcement officers as being under the influence – averaging 38 crashes per month. The frequency of underage-driver crashes also tracked compliance check frequency over time: Crashes in this age-group declined during the first wave of compliance check enforcement, increased (after a lag) when enforcement declined, and declined again after 2010 when enforcement increased. In contrast to the decline in crashes among drivers under 21, alcohol-related crashes among drivers aged 21+ trended upwards between 2011 and 2016. Statistical modeling indicated that over the 78 months of stable compliance checks (2010 to 2016), AET enforcement led to a decline in underage drink-driver crashes of 18-29% (depending on the method used to identify alcohol-involved crashes) compared to the pre-2010 period of inconsistent compliance. This impact was statistically significant.

Implementation of the AET compliance check program in 2006 was followed by a dramatic decline in rates of underage drinking among South Carolina youth, which continued over the next 10 years. Overall, the study provides strong evidence that consistent and regular retail compliance check enforcement can result in sustained reductions in alcohol availability to under-21s, sufficient to reduce alcohol-related traffic crashes in this age group. The researchers are not aware of any other state having duplicated the South Carolina AET program.

Alcohol compliance checks and underage alcohol-involved crashes: Evaluation of a state-wide enforcement program in South Carolina 2006-2016.

M. D. George, R. Holder, S. Shamblen, M. M. Nienhius, H. D. Holder (pages xxx).