Toward improved evaluations of laws against drink-driving
Authors: Etienne Blais, Pierre Maurice
Journal: The Lancet (2018)

On Dec 5, 2014, Scotland lowered the legal blood alcohol concentration (BAC) limit for driving to 0·05 g/dL. In The Lancet, Houra Haghpanahan and colleagues1Haghpanahan H Lewsey J Mackay DF et al.An evaluation of the effects of lowering blood alcohol concentration limits for drivers on the rates of road traffic accidents and alcohol consumption: a natural experiment.Lancet. 2018; (published online Dec 12.)http://dx.doi.org/10.1016/S0140-6736(18)32850-2Summary Full Text Full Text PDF PubMed Scopus (30) Google Scholar report their study using data from Scotland (the intervention group) and England and Wales (the control group) for the period from Jan 1, 2013, to Dec 31, 2016, to assess the effect of this change on frequency of road traffic accidents (RTAs) and on alcohol consumption. Their evaluation indicates that the reduced BAC limit in Scotland was not associated with a decline in RTAs (rate ratio 1·07, 95% CI 0·98 to 1·17; p=0·10), and did not affect alcohol sales in grocery and convenience stores (off-trade sales −0·3%, 95% CI −1·7 to 1·1; p=0·71). However, a slight but statistically significant decrease was observed for alcohol sales in bars and restaurants (on-trade sales −0·7%, −0·8 to −0·5; p<0·0001).1Haghpanahan H Lewsey J Mackay DF et al.An evaluation of the effects of lowering blood alcohol concentration limits for drivers on the rates of road traffic accidents and alcohol consumption: a natural experiment.Lancet. 2018; (published online Dec 12.)http://dx.doi.org/10.1016/S0140-6736(18)32850-2Summary Full Text Full Text PDF PubMed Scopus (30) Google Scholar The assessment of Scotland's new BAC law rests on a robust, comparative, interrupted time-series design and, accordingly, the results show strong internal validity. However, the findings deviate from the general evidence that lowering the BAC limit for driving prevents alcohol-related RTAs.2Fell JC Scherer M Estimation of the potential effectiveness of lowering the blood alcohol concentration (BAC) limit for driving from 0·08 to 0·05 grams per deciliter in the United States.Alcohol Clin Exp Res. 2017; 41: 2128-2139Crossref PubMed Scopus (27) Google Scholar, 3Mann RE Macdonald S Stoduto G Bondy S Jonah B Shaikh A The effects of introducing or lowering legal per se blood alcohol limits for driving: an international review.Accid Anal Prev. 2001; 33: 569-583Crossref PubMed Scopus (135) Google Scholar Results from Haghpanahan and colleagues' study also question the relevance of a recent recommendation to introduce a 0·05 g/dL limit in England,4Burton R Henn C Lavoie D et al.A rapid evidence review of the effectiveness and cost-effectiveness of alcohol control policies: an English perspective.Lancet. 2017; 389: 1558-1580Summary Full Text Full Text PDF PubMed Scopus (172) Google Scholar which is estimated to potentially save about 25 lives and prevent 100 serious traffic injuries per year. Law or programme evaluations are generally supported by a theory of change, which takes the form of an explicit model explaining how the intervention is expected to produce the intended outcomes. The theory of change guides the evaluation.5Coryn CL Noakes LA Westine CD Schröter DC A systematic review of theory-driven evaluation practice from 1990 to 2009.Am J Eval. 2011; 32: 199-226Crossref Scopus (243) Google Scholar, 6Campbell M Fitzpatrick R Haines A et al.Framework for design and evaluation of complex interventions to improve health.BMJ. 2000; 321: 694-696Crossref PubMed Scopus (2372) Google Scholar Results from the Scottish experiment1Haghpanahan H Lewsey J Mackay DF et al.An evaluation of the effects of lowering blood alcohol concentration limits for drivers on the rates of road traffic accidents and alcohol consumption: a natural experiment.Lancet. 2018; (published online Dec 12.)http://dx.doi.org/10.1016/S0140-6736(18)32850-2Summary Full Text Full Text PDF PubMed Scopus (30) Google Scholar call for additional evaluations based on advanced theories of change, especially in an era in which several improvements in alcohol-related RTAs have been achieved. Evaluations of BAC laws should shift their focus from what works to how it works. Theories of change are usually used to justify the introduction of new prevention programmes known for their effectiveness. However, the main propositions in theories of change need to be empirically challenged.7Chen HT Theory-driven evaluations. Sage, Newbury Park, CA1990Google Scholar The effectiveness of BAC laws is mainly embedded in deterrence:8Shults RA Elder RW Sleet DA et al.Reviews of evidence regarding interventions to reduce alcohol-impaired driving.Am J Prev Med. 2001; 21: 66-88Summary Full Text Full Text PDF PubMed Scopus (509) Google Scholar sanctions and other negative consequences prescribed by the law should deter people from drink-driving. According to this logic, BAC laws must be enforced and publicised to change outcomes in the short-term (ie, risk perceptions and attitudes toward drink-driving), intermediate-term (ie, strategies adopted to avoid drink-driving), and long-term (ie, RTAs).9Tippetts AS Voas RB Fell JC Nichols JL A meta-analysis of ·08 BAC laws in 19 jurisdictions in the United States.Accid Anal Prev. 2005; 37: 149-161Crossref PubMed Scopus (88) Google Scholar Most studies focus on RTAs and neglect to investigate the implementation of, and processes associated with, BAC laws.2Fell JC Scherer M Estimation of the potential effectiveness of lowering the blood alcohol concentration (BAC) limit for driving from 0·08 to 0·05 grams per deciliter in the United States.Alcohol Clin Exp Res. 2017; 41: 2128-2139Crossref PubMed Scopus (27) Google Scholar Haghpanahan and colleagues are among the few to estimate changes in on-trade alcohol sales after the introduction of the new BAC law. A decline in alcohol consumption, however, represents just one possible mechanism that could trigger a decrease in alcohol-related RTAs.8Shults RA Elder RW Sleet DA et al.Reviews of evidence regarding interventions to reduce alcohol-impaired driving.Am J Prev Med. 2001; 21: 66-88Summary Full Text Full Text PDF PubMed Scopus (509) Google Scholar People might also change their drinking habits: for example, they could drink over longer periods to respect the new BAC limit. Furthermore, improved evaluations will only be possible if theories of change incorporate assumptions about situations in which BAC laws can be ineffective or produce backlash effects.10Blais É Bellavance F Marcil A Carnis L Effects of introducing an administrative ·05% blood alcohol concentration limit on law enforcement patterns and alcohol-related collisions in Canada.Accid Anal Prev. 2015; 82: 101-111Crossref PubMed Scopus (21) Google Scholar For example, there might be specific defiance by individuals and general defiance by collectives, referring to situations in which sanctions are perceived as unfair and excessive. Fairness and legitimacy are two necessary conditions for criminal sanctions to lower, and not increase, offences.11Sherman LW Defiance, deterrence, and irrelevance: a theory of the criminal sanction.J Res Crime Delinq. 1993; 30: 445-473Crossref Scopus (751) Google Scholar, 12Bates LJ Antrobus E Bennett S Martin P Comparing police and public perceptions of a routine traffic encounter.Police Q. 2015; 18: 442-468Crossref Scopus (24) Google Scholar Furthermore, compliance with BAC laws increases when people are aware of—and offered—legitimate alternatives to drink-driving.13Grube JW Voas RB Predicting underage drinking and driving behaviors.Addiction. 1996; 91: 1843-1857Crossref PubMed Scopus (65) Google Scholar Therefore, a deficient public transportation system or the absence of designated driver programmes could partly explain the ineffectiveness of a BAC law. Future evaluations of BAC laws also need to account for organisational contexts in their theory of change.9Tippetts AS Voas RB Fell JC Nichols JL A meta-analysis of ·08 BAC laws in 19 jurisdictions in the United States.Accid Anal Prev. 2005; 37: 149-161Crossref PubMed Scopus (88) Google Scholar A programme implemented with high fidelity is generally successful. Inadequate enforcement and publicity might explain the failure of the law in Scotland seen in Haghpanahan and colleagues' study, but information on such activities is not provided in the Article. A parallel study is underway to explore Scotland's BAC limit change from the perspective of the public, police, and alcohol retailers. This upcoming study will also examine the magnitude of enforcement efforts (eg, indicators on sobriety checkpoints, arrests, and drivers tested) and public campaigning to better understand these results. Ensuring programme fidelity requires planning and monitoring activities to ensure that all partners fulfil their duty in a timely manner. Thus, future research needs to provide information about strategies used to implement and coordinate various advertisement and enforcement activities.9Tippetts AS Voas RB Fell JC Nichols JL A meta-analysis of ·08 BAC laws in 19 jurisdictions in the United States.Accid Anal Prev. 2005; 37: 149-161Crossref PubMed Scopus (88) Google Scholar The best evidence indicates that new BAC laws prevent RTAs when they are effectively enforced (meaning that resources are required to conduct highly visible enforcement activities) and are supported by public communication campaigns. Other legal initiatives (eg, random breath testing) and public education initiatives generally enhance the safety effects of BAC laws.2Fell JC Scherer M Estimation of the potential effectiveness of lowering the blood alcohol concentration (BAC) limit for driving from 0·08 to 0·05 grams per deciliter in the United States.Alcohol Clin Exp Res. 2017; 41: 2128-2139Crossref PubMed Scopus (27) Google Scholar, 3Mann RE Macdonald S Stoduto G Bondy S Jonah B Shaikh A The effects of introducing or lowering legal per se blood alcohol limits for driving: an international review.Accid Anal Prev. 2001; 33: 569-583Crossref PubMed Scopus (135) Google Scholar, 8Shults RA Elder RW Sleet DA et al.Reviews of evidence regarding interventions to reduce alcohol-impaired driving.Am J Prev Med. 2001; 21: 66-88Summary Full Text Full Text PDF PubMed Scopus (509) Google Scholar The Scottish experiment, however, shows that additional research is needed to identify essential components of effective BAC laws according to different contexts. Evaluations based on improved theories of change could lead to better understanding of how BAC laws change behaviours and how they can be implemented with high fidelity. We declare no competing interests. We thank Katherine Pendakis for her help in preparing this Comment. An evaluation of the effects of lowering blood alcohol concentration limits for drivers on the rates of road traffic accidents and alcohol consumption: a natural experimentLowering the driving BAC limit to 0·05 g/dL from 0·08 g/dL in Scotland was not associated with a reduction in RTAs, but this change was associated with a small reduction in per-capita alcohol consumption from on-trade alcohol sales. One plausible explanation is that the legislative change was not suitably enforced—for example with random breath testing measures. Our findings suggest that changing the legal BAC limit for drivers in isolation does not improve RTA outcomes. These findings have significant policy implications internationally as several countries and jurisdictions consider a similar reduction in the BAC limit for drivers. Full-Text PDF Open Access