Can progress in reducing alcohol-impaired driving fatalities be resumed? Results of a workshop sponsored by the Transportation Research Board, Alcohol, Other Drugs, and Transportation Committee (ANB50)

Effectiveness of road safety interventions: An evidence and gap map

Background

Road Traffic injuries (RTI) are among the top ten leading causes of death in the world resulting in 1.35 million deaths every year, about 93% of which occur in low- and middle-income countries (LMICs). Despite several global resolutions to reduce traffic injuries, they have continued to grow in many countries. Many high-income countries have successfully reduced RTI by using a public health approach and implementing evidence-based interventions. As many LMICs develop their highway infrastructure, adopting a similar scientific approach towards road safety is crucial. The evidence also needs to be evaluated to assess external validity because measures that have worked in high-income countries may not translate equally well to other contexts. An evidence gap map for RTI is the first step towards understanding what evidence is available, from where, and the key gaps in knowledge.

Objectives

The objective of this evidence gap map (EGM) is to identify existing evidence from all effectiveness studies and systematic reviews related to road safety interventions. In addition, the EGM identifies gaps in evidence where new primary studies and systematic reviews could add value. This will help direct future research and discussions based on systematic evidence towards the approaches and interventions which are most effective in the road safety sector. This could enable the generation of evidence for informing policy at global, regional or national levels.

Search Methods

The EGM includes systematic reviews and impact evaluations assessing the effect of interventions for RTI reported in academic databases, organization websites, and grey literature sources. The studies were searched up to December 2019.

Selection Criteria

The interventions were divided into five broad categories: (a) human factors (e.g., enforcement or road user education), (b) road design, infrastructure and traffic control, (c) legal and institutional framework, (d) post-crash pre-hospital care, and (e) vehicle factors (except car design for occupant protection) and protective devices. Included studies reported two primary outcomes: fatal crashes and non-fatal injury crashes; and four intermediate outcomes: change in use of seat belts, change in use of helmets, change in speed, and change in alcohol/drug use. Studies were excluded if they did not report injury or fatality as one of the outcomes.

Data Collection and Analysis

The EGM is presented in the form of a matrix with two primary dimensions: interventions (rows) and outcomes (columns). Additional dimensions are country income groups, region, quality level for systematic reviews, type of study design used (e.g., case-control), type of road user studied (e.g., pedestrian, cyclists), age groups, and road type. The EGM is available online where the matrix of interventions and outcomes can be filtered by one or more dimensions. The webpage includes a bibliography of the selected studies and titles and abstracts available for preview. Quality appraisal for systematic reviews was conducted using a critical appraisal tool for systematic reviews, AMSTAR 2.

Main Results

The EGM identified 1859 studies of which 322 were systematic reviews, 7 were protocol studies and 1530 were impact evaluations. Some studies included more than one intervention, outcome, study method, or study region. The studies were distributed among intervention categories as: human factors (n = 771), road design, infrastructure and traffic control (n = 661), legal and institutional framework (n = 424), post-crash pre-hospital care (n = 118) and vehicle factors and protective devices (n = 111). Fatal crashes as outcomes were reported in 1414 records and non-fatal injury crashes in 1252 records. Among the four intermediate outcomes, speed was most commonly reported (n = 298) followed by alcohol (n = 206), use of seatbelts (n = 167), and use of helmets (n = 66). Ninety-six percent of the studies were reported from high-income countries (HIC), 4.5% from upper-middle-income countries, and only 1.4% from lower-middle and low-income countries. There were 25 systematic reviews of high quality, 4 of moderate quality, and 293 of low quality.

Authors' Conclusions

The EGM shows that the distribution of available road safety evidence is skewed across the world. A vast majority of the literature is from HICs. In contrast, only a small fraction of the literature reports on the many LMICs that are fast expanding their road infrastructure, experiencing rapid changes in traffic patterns, and witnessing growth in road injuries. This bias in literature explains why many interventions that are of high importance in the context of LMICs remain poorly studied. Besides, many interventions that have been tested only in HICs may not work equally effectively in LMICs. Another important finding was that a large majority of systematic reviews are of low quality. The scarcity of evidence on many important interventions and lack of good quality evidence-synthesis have significant implications for future road safety research and practice in LMICs. The EGM presented here will help identify priority areas for researchers, while directing practitioners and policy makers towards proven interventions.

"Residual blood THC levels in frequent cannabis users after over four hours of abstinence: A systematic review."

BACKGROUND

Tetrahydrocannabinol (THC), the primary psychoactive component of cannabis, causes psychomotor impairment and puts drivers at increased risk of motor vehicle collisions. Many jurisdictions have per se limits for THC, often 2 or 5 ng/mL, that make it illegal to drive with THC above the "legal limit". People who use cannabis regularly develop partial tolerance to some of its impairing effects. Regular cannabis users may also have persistent elevation of THC even after a period of abstinence. Some stakeholders worry that current per se limits may criminalize unimpaired drivers simply because they use cannabis. We conducted a systematic review of published literature to investigate residual blood THC concentrations in frequent cannabis users after a period of abstinence.

METHODS

We identified relevant articles by combining terms for "cannabis" and "blood" and "concentration" and "abstinence" and searching MEDLINE, EMBASE, PsycINFO, and Web of Science. We included studies that reported THC levels in frequent cannabis users after more than 4 h of abstinence.

RESULTS

Our search identified 1612 articles of which 8 met our inclusion criteria. After accounting for duplicate publications, we had identified 6 independent studies. These studies show that blood THC over 2 ng/mL does do not necessarily indicate recent cannabis use in frequent cannabis users. Five studies reported blood THC >2 ng/mL (or plasma THC >3 ng/mL) in some participants after six days of abstinence and two reported participants with blood THC >5 ng/mL (or plasma THC > 7.5 ng/mL) after a day of abstinence.

CONCLUSIONS

Blood THC >2 ng/mL, and possibly even THC >5 ng/mL, does not necessarily represent recent use of cannabis in frequent cannabis users.

Effect of Lowering the Blood Alcohol Concentration Limit to 0.03 Among Hospitalized Trauma Patients in Southern Taiwan: A Cross-Sectional Analysis

Background

In June 2013, the legal blood alcohol concentration (BAC) limit for driving was lowered from 0.05 to 0.03 mg/mL in Taiwan. Thus, this study aimed to assess the epidemiological changes in terms of drinking among drivers in southern Taiwan before and after the law was imposed.

Methods

Only patients who had undergone the BAC test at the emergency room were included in the study. The patients during the study period before (n = 2735) and after (n = 2413) the implementation of the law were selected for comparison. Drunk patients were defined as those who had a BAC ≥0.005 and were considered as driving under the influence (DUI) of alcohol. Meanwhile, driving while intoxicated (DWI) was defined as a BAC ≥0.05, which was the level adopted in the new law.

Results

Since the BAC limit lowered to 0.03, the number of DUI patients significantly decreased from 340 (12.4%) to 171 (7.1%), and that of DWI patients significantly reduced from 273 (10.0%) to 146 (6.1%) based on the alcohol test. In addition, after the implementation of the law, the number of associated injuries did not significantly decrease from that before the law was implemented in patients involved in alcohol-related crashes.

Conclusion

After lowering the legal BAC limit from 0.05 to 0.03, responsiveness to the change in law was observed among the studied population. However, such responsiveness may not be observed in some citizens who may need special interventions to help reduce their behavior of drinking and driving.

Underutilized strategies in traffic safety: Results of a nationally representative survey

Objective: Numerous strategies proven to be effective in reducing crash fatalities have been underutilized in the United States, including sobriety checkpoints; automated enforcement; lower blood alcohol concentration (BAC) limits; primary enforcement of safety belt and motorcycle helmet use laws; alcohol ignition interlock installations; drugged driving screening; lowered residential speed limits; and roundabout installations. If these strategies are implemented widely in every state, traffic fatalities could be reduced by at least 50%. A barrier to implementation is the perception by officials that the public is against them. The purpose of this study was to determine which of these underutilized measures would be favorable to the American public given that they are educated on the research of their effectiveness.Methods: A representative survey of 2,000 U.S. drivers was conducted in October 2018 with 30 questions about these underutilized strategies using the National Opinion Research Center's (NORC) AmeriSpeak® survey instrument. Our objective was to gauge the public's opinion of these strategies when they are aware of the research on their effectiveness.Results: Respondents were given a summary of the research on the effectiveness of these strategies and then asked whether they were in favor of them in their communities; 64.7% of the respondents were in favor of conducting sobriety checkpoints at least monthly; 68.2% were in favor of police using passive alcohol sensors at sobriety checkpoints; 60.3% of respondents were in favor of using speed and red light cameras for automated enforcement; 70.1% were in favor of a law that required all cars to have seat belt reminders that continuously chime until the seat belt is buckled, including for rear seat passengers; and 62.5% were in favor of raising the fine in their state for not using a seat belt from $25 to $100. Other results indicated public support for these strategies.Conclusions: The results indicate that when drivers in the United States are given facts about certain strategies to reduce crash fatalities, the majority are in favor of the underutilized strategies. This information could be useful to legislators and highway safety officials in their decisions to implement these strategies.

Motivational factors associated with drowsy driving behavior: a qualitative investigation of college students

OBJECTIVES

This qualitative investigation sought to identify the motivational factors that contribute to drowsy driving in college students and to discover important messaging strategies that may help prevent or reduce this behavior in this population.

DESIGN

Four focus groups of college students.

SETTING

A large university in the Washington, DC, metropolitan area during the Fall 2016 term.

PARTICIPANTS

Twenty-six undergraduate students between the ages of 18 and 25 years.

MEASUREMENTS

Notes and transcripts from the focus group sessions were analyzed to identify recurring themes regarding attitudes, motivations, experiences, influences, and potential preventive messaging strategies related to drowsy driving.

RESULTS

Although most participants had heard of drowsy driving and were concerned about it, they did not associate it with legal risks and were more concerned about alcohol-impaired and distracted driving as crash risks. Participants viewed drowsy driving as a normal and unavoidable part of their lives over which they had little control. For potential anti-drowsy driving messaging strategies, participants preferred messages delivered via audiovisual or social media that featured graphic and emotional portrayals of crashes and their consequences. Participants also voiced strong support for preventive messaging strategies equating various degrees of sleep deprivation to known impairing levels of alcohol, as well as messages providing cues to action to actual drowsy drivers on roadways.

CONCLUSIONS

Increased enforcement, education, and public messaging campaigns are needed to increase knowledge and influence attitudes and opinions among young drivers about the dangers and social unacceptability of drowsy driving.

Canadian drivers' attitudes regarding preventative responses to driving while impaired by alcohol

BACKGROUND

In many jurisdictions, a risk assessment following a first driving while impaired (DWI) offence is used to guide administrative decision making regarding driver relicensing. Decision error in this process has important consequences for public security on one hand, and the social and economic well being of drivers on the other. Decision theory posits that consideration of the costs and benefits of decision error is needed, and in the public health context, this should include community attitudes. The objective of the present study was to clarify whether Canadians prefer decision error that: i) better protects the public (i.e., false positives); or ii) better protects the offender (i.e., false negatives).

METHODS

A random sample of male and female adult drivers (N=1213) from the five most populated regions of Canada was surveyed on drivers' preference for a protection of the public approach versus a protection of DWI drivers approach in resolving assessment decision error, and the relative value (i.e., value ratio) they imparted to both approaches. The role of region, sex and age on drivers' value ratio were also appraised.

RESULTS

Seventy percent of Canadian drivers preferred a protection of the public from DWI approach, with the overall relative ratio given to this preference, compared to the alternative protection of the driver approach, being 3:1. Females expressed a significantly higher value ratio (M=3.4, SD=3.5) than males (M=3.0, SD=3.4), p<0.05. Regression analysis showed that both days of alcohol use in the past 30days (CI for B: -0.07, -0.02) and frequency of driving over legal BAC limits in the past year (CI for B=-0.19, -0.01) were significantly but modestly related to lower value ratios, R²(adj.)=0.014, p<0.001. Regional differences were also detected.

CONCLUSIONS

Canadian drivers strongly favour a protection of the public approach to dealing with uncertainty in assessment, even at the risk of false positives. Accounting for community attitudes concerning DWI prevention and the individual differences that influence them could contribute to more informed, coherent and effective regional policies and prevention program development.

Effect of Maryland's 2011 Alcohol Sales Tax Increase on Alcohol-Positive Driving

INTRODUCTION

The 2011 Maryland alcohol sales tax increase from 6% to 9% provided an opportunity to evaluate the impact on rates of alcohol-positive drivers involved in injury crashes.

METHODS

Maryland police crash reports from 2001 to 2013 were analyzed using an interrupted time series design and a multivariable analysis employing generalized estimating equations models with a negative binomial distribution. Data were analyzed in 2014-2015.

RESULTS

There was a significant gradual annual reduction of 6% in the population-based rate of all alcohol-positive drivers (p<0.03), and a 12% reduction for drivers aged 15-20 years (p<0.007), and 21-34 years (p<0.001) following the alcohol sales tax increase. There were no significant changes in rates of alcohol-positive drivers aged 35-54 years (rate ratio, 0.98; 95% CI=0.89, 1.09). Drivers aged ≥55 years had a significant immediate 10% increase in the rate of alcohol-positive drivers (rate ratio, 1.10; 95% CI=1.04, 1.16) and a gradual increase of 4.8% per year after the intervention. Models using different denominators and controlling for multiple factors including a proxy for unmeasured factors found similar results overall.

CONCLUSIONS

The 2011 Maryland alcohol sales tax increase led to a significant reduction in the rate of all alcohol-positive drivers involved in injury crashes especially among drivers aged 15-34 years. This is the first study to examine the impact of alcohol sales taxes on crashes; previous research focused on excise tax. Increasing alcohol taxes is an important but often neglected intervention to reduce alcohol-impaired driving.