Best practices to navigating absence of alcohol-related outcomes in traffic studies: a systematic review

Author(s): Joseph, Martinez Diaz, Nazif-Munoz

Slidedeck Presentation:




Alcohol policies might ultimately reduce the number of people driving while intoxicated. Thus, having significant road safety implications. While alcohol-related traffic outcomes (e.g., blood alcohol concentration in drivers) is the standard of reference in the assessment of alcohol policies impacts within the road safety domain, usually this information – for practical or technical reasons – is not available to researchers across the globe. We are interested in knowing how researchers worldwide have solved this issue.


To systematically review the published evidence assessing alcohol policies' road safety implications when alcohol information for traffic outcomes is absent.


We conducted a systematic review of studies assessing alcohol policies' road safety implications. Eligibility criteria for studies were: 1) participants: road users (i.e., passengers, pedestrians, or drivers of any type of vehicle); 2) intervention: alcohol policies aimed to deter drinking and driving (e.g., laws concerning blood alcohol content, license suspension, mandatory education, and vehicle ignition interlock); 3) comparator: absence of alcohol policies (e.g., pre-intervention period or another jurisdiction where legislation was not applied); 4) outcomes: road traffic injuries and deaths; and 4) study design: quasi-experimental (e.g., interrupted time series, difference-in-differences, and synthetic controls) or observational (i.e., retrospective and prospective cohorts, and case controls) studies. We excluded studies reporting access to alcohol information for traffic outcomes (e.g., blood alcohol concentration in drivers). Systematic reviews, meta-analyses, editorials, case studies, and case series were also excluded. Searches were conducted in PsycInfo, CINAHL Plus, Medline, and SocIndex databases from 2000 onwards, with no limit on language. Two researchers selected the studies and extracted data independently, with disagreements solved through discussion and involvement of a third party. The data were synthesized using a narrative approach and comparative tables.


After initially identifying 2,539 records, the selection process led to the inclusion of 27 studies. Most studies were conducted in the United States – either by having information for all or some of its jurisdictions. The most used study design was interrupted time series. A wide range of alcohol policies aimed to deter drinking and driving were assessed (e.g., introducing random breath testing, license suspension, and vehicle impounding based on roadside breath alcohol analysis results, lowering the blood alcohol concentration limit, underage alcohol laws, etc.). Most studies used data for drivers of any type of vehicle. The most cited rationale for not using alcohol information related to traffic outcomes was that this data type was not available. Surrogate measures commonly used were traffic injuries or fatalities for the whole population under study or single-vehicle nighttime crashes. In general, the alcohol policies were associated with improved road safety outcomes.


Studies, mostly from developed countries, have used traffic injuries or fatalities for the whole road user population as surrogate measures to assess the impact of alcohol policies on road traffic outcomes.


We are in need of developing better conditions for tracking alcohol-related outcomes and to advance on scoping methods that allow estimating improvement scenarios for this type of outcome when these are absent.