Effectiveness of lowering the blood alcohol concentration (BAC) limit for driving from 0.10 to 0.08 grams per deciliter in the United States

2019-03-19T16:12:55Z (GMT) by Michael Scherer James C. Fell

Objective: The current study evaluates of the effects of lowering the blood alcohol concentration (BAC) limit from 0.10 to 0.08 g/dL across all 50 states in the United States. Our objectives were to (1) estimate the effects of the 0.08 g/dL BAC limit on drinking driver fatal crash rates; (2) compare the effects from early-adopting states to the effects of late-adopting states; (3) determine the effects on drivers with low BACs (0.01–0.07 g/dL) and high BACs (0.08+ g/dL); and (4) estimate the lives saved since 1983 due to the adoption of 0.08 g/dL BAC laws.

Methods: Our study examined annual data from the Fatality Analysis Reporting System (FARS) for each jurisdiction from 1982 through 2014. Our basic outcome measure was the ratio of drinking drivers (BAC ≥0.01 g/dL) to nondrinking drivers (BAC = 0.00 g/dL). Covariates included 0.10 BAC laws, administrative license revocation (ALR) laws, seat belt laws, minimum legal drinking age (MLDA) laws, and unemployment rates. We utilized autoregressive integrated moving average (ARIMA) models for each state, where the implementation date of the law was modeled as a zero-order transfer function in the series, in addition to any extant trends that may have been occurring simultaneously. Before determining the specific impact of the implementation of 0.08 g/dL BAC laws, we conducted a time series analysis for each state. We tested for between-state mediating factors relating to our covariates.

Results: A total of 38 of the 51 jurisdictions showed that lowering the BAC limit was associated with reduced drinking driver fatal crash ratios, with 20 of those reductions being significant. The total effects showed a 10.4% reduction in annual drinking driver fatal crash rates, which is estimated to have saved an average of 1,736 lives each year between 1983 and 2014 and 24,868 lives in total. Implementing a BAC limit of 0.08 g/dL had significant impacts on both high- and low-BAC fatal crash ratios. Though early-adopting jurisdictions (1983–1999) demonstrated a larger decrease in fatal drinking driver crash ratios than did late-adopting jurisdictions (2000–2005), the results were not statistically significant (P > .05).

Conclusions: Our study of the effects of lowering the BAC from 0.10 to 0.08 g/dL in the United States from 1982 to 2014 showed an overall effect of 10.4% on annual drinking driver fatal crash rates, in line with other multistate studies. This research provides strong evidence of the relationship between lowering the BAC limit for driving and the general deterrent effect on impaired-driving fatal crash rates.