Alcohol Compliance Checks and Underage Alcohol-Involved Crashes: Evaluation of a Statewide Enforcement Program in South Carolina from 2006 to 2016.
OBJECTIVE
This research evaluated the South Carolina Alcohol Enforcement Team impact for reducing retail alcohol access to underage persons to decrease drinking and driving crashes among that population.


METHODS
The natural research experiment used interrupted time-series (ITS) analyses of drinking and driving crashes involving under 21-year-old drivers from July 2006 through December 2016 (126-month period = 4,782 Driving Under Influence [DUI] crashes for under 21-year-old drivers, µ = 38 crashes per month). Additional data analyzed included the monthly total number of retail compliance checks (total during 126-month period = 64,954 compliance checks completed, µ = 515.5 checks per month), the average percentage of underage alcohol purchases (total completed during 126-month period = 8,814 purchases, µ = 70 purchases per month), and a calculated measure of the percent of the population under 21 years old exposed to compliance checks each month. We used drinking and driving crashes for 21-year-old and over drivers as a control time series (total number over a 126-month period = 52,180 DUI crashes for 21 and older drivers, µ = 414.1 crashes per month).


RESULTS
The results show a decline in drinking and driving crashes for drivers under 21 when compliance checks increase, and when compliance checks decline, traffic crashes increase. Stable Alcohol Enforcement Team implementation over 78 months produced an overall 18 to 29% decline in such crashes. A visual examination of the crash time series demonstrated that under-21-age-driver crashes declined during the first wave of implementation and increased following a lag when enforcement declined, which provided additional empirical support for a South Carolina Alcohol Enforcement Team impact on retail alcohol availability. An ITS analysis of the prestable period compared to the stable period was statistically significant (T = -3.78, p < 0.001). A cross-check of these results using single-vehicle nighttime crashes using identical Autoregressive Integrated Moving Average models was also statistically significant (T = -8.18, p < 0.001).


CONCLUSIONS
This longitudinal study provides strong evidence of sustained reductions in alcohol availability to underage youth can subsequently reduce alcohol-related traffic crashes. Reductions found in this study continued over several years, considerably longer than any previous equivalent research has shown.