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There is a growing interest in how extensively the use of marijuana by drivers relates to crash involvement. While cognitive, lab-based studies are consistent in showing that the use of cannabis impairs driving tasks, epidemiological, field-based studies have been inconclusive regarding whether cannabis use causes an increased risk of accidents. There is ample evidence that the presence of cannabis among drivers with a BAC≥0.08g/dL highly increases the likelihood of a motor vehicle crash. Less clear, however, is the contribution of cannabis to crash risk when drivers have consumed very little or no alcohol. This effort addresses this gap in knowledge. We took advantage of a unique database that merged fatal crashes in the California Statewide Integrated Traffic Records System (SWITRS) and the Fatality Analysis Reporting System (FARS), which allows for a precise identification of crash responsibility. To account for recent increase in lab testing, we restricted our sample to cover only the years 1993-2009. A total of 4294 drivers were included in the analyses. Descriptive analyses and logistic regressions were run to model the contribution of alcohol and drugs to the likelihood of being responsible in a fatal crash. We found evidence that compared with drivers negative for alcohol and cannabis, the presence of cannabis elevates crash responsibility in fatal crashes among drivers at zero BACs (OR=1.89) and with 0BAC0.05g/dL (OR=3.42), suggesting that emphasis on curbing impaired driving should not be solely focused on heavy-drinking drivers. Data limitations however caution about the generalizability of study findings. Special efforts to understand the effect of cannabis on fatal crashes, in particular in the absence of alcohol, are needed.

Research measuring levels of enforcement has investigated whether increases in police activities (e.g., checkpoints, driving-while-intoxicated [DWI] special patrols) above some baseline level are associated with reduced crashes and fatalities. Little research, however, has attempted to quantitatively measure enforcement efforts and relate different enforcement levels to specific levels of the prevalence of alcohol-impaired driving.The objective of this study was to investigate the effects of law-enforcement intensity in a sample of communities on the rate of crashes involving a drinking driver. We analyzed the influence of different enforcement strategies and measures: (1) specific deterrence - annual number of driving-under-the-influence (DUI) arrests per capita; (2) general deterrence - frequency of sobriety checkpoint operations; (3) highly visible traffic enforcement - annual number of traffic stops per capita; (4) enforcement presence - number of sworn officers per capita; and (5) overall traffic enforcement - the number of other traffic enforcement citations per capita (i.e., seat belt citations, speeding tickets, and other moving violations and warnings) in each community.We took advantage of nationwide data on the local prevalence of impaired driving from the 2007 National Roadside Survey (NRS), measures of DUI enforcement activity provided by the police departments that participated in the 2007 NRS, and crashes from the General Estimates System (GES) in the same locations as the 2007 NRS. We analyzed the relationship between the intensity of enforcement and the prevalence of impaired driving crashes in 22-26 communities with complete data. Log-linear regressions were used throughout the study.A higher number of DUI arrests per 10,000 driving-aged population was associated with a lower ratio of drinking-driver crashes to non-drinking-driver crashes (p=0.035) when controlling for the percentage of legally intoxicated drivers on the roads surveyed in the community from the 2007 NRS. Results indicate that a 10% increase in the DUI arrest rate is associated with a 1% reduction in the drinking driver crash rate. Similar results were obtained for an increase in the number of sworn officers per 10,000 driving-age population.While a higher DUI arrest rate was associated with a lower drinking-driver crash rate, sobriety checkpoints did not have a significant relationship to drinking-driver crashes. This appeared to be due to the fact that only 3% of the on-the-road drivers were exposed to frequent sobriety checkpoints (only 1 of 36 police agencies where we received enforcement data conducted checkpoints weekly). This low-use strategy is symptomatic of the general decline in checkpoint use in the U.S. since the 1980s and 1990s when the greatest declines in alcohol-impaired-driving fatal crashes occurred. The overall findings in this study may help law enforcement agencies around the country adjust their traffic enforcement intensity in order to reduce impaired driving in their community.

There is an increasing number of motor vehicle crashes (MVCs) in the U.S. that occur at intersections. Noncompliance with traffic signals is one of the causes for such increase. In this study, we focused on Hispanic drivers. It has been shown that failing to follow traffic laws and regulations is a major cause of MVCs in Latin America. Does this driving behavior in Latin America correspond to the Hispanic community in the U.S.? Are U.S. Hispanics more likely to die in a red light incident? Are Hispanics more likely to be red light runners than other racial/ethnic groups in the U.S.? We answered these questions by taking advantage of a 1990-1996 Fatality Analysis Reporting System (FARS) file with additional racial/ethnic information. Overall, we found no differences between African-American, White, and Hispanic drivers regarding red light running. We found that drinking and driving was the most important factor for red light running. However, we found evidence that some Hispanic subgroups may be more vulnerable to red light running. One such subgroup is formed by Hispanics who have no valid driver license and no record of previous driver license suspension. This study is the first to apply national, archival data to document the relevance of race/ethnicity to the red light running problem, and we hope that it might serve as an incentive for more research on this area.

More than a dozen studies on the effectiveness of the .08 blood alcohol concentration (BAC) laws have been published; however, those studies have varied both in the statistical methods and the type of outcome measure used, so it is difficult to integrate the findings into an overall estimate of the effectiveness of the law. This study used a consistent outcome measure, drinking drivers in fatal crashes and an identical methodology time-series analysis, to analyze the introduction of the .08 law in 18 states and the District of Columbia from 1982 to 2000. Each analysis accounted for other key safety laws (administrative license suspension/revocation and safety belt laws), as well as economic conditions that might influence the effectiveness of the .08 law. This provided 19 independent evaluations in which the effectiveness (treatment effect) of the law could be measured in the same quantitative terms. The number of drinking drivers in fatal crashes declined in 16 of the 19 jurisdictions after the .08 law was adopted. Nine of the 16 reductions were statistically significant (p < .05). The effect size combined across all 19 locations showed statistically significant decline (p < .005) of 14.8% in the rate of drinking drivers in fatal crashes after the .08 laws were introduced. The reduction was greater in states that had an administrative license suspension/revocation law and implemented frequent sobriety checkpoints. This analysis suggests that 947 lives might have been saved, had all 50 states and the District of Columbia had the .08 law throughout the year 2000.

The objective of this research was to determine the extent to which the decline in alcohol-related highway deaths among drivers younger than age 21 years can be attributed to raising the minimum legal drinking age (MLDA) and establishing zero tolerance (0.02% blood alcohol concentration (BAC) limit for drivers younger than age 21 years) laws. Data on all drivers younger than age 21 years involved in fatalities in the United States from 1982 to 1997 were used in the study. Quarterly ratios of BAC-positive to BAC-negative drivers in each of the 50 states where analyzed in a pooled cross-sectional time-series analysis. After accounting for differences among the 50 states in various background factors, changes in economic and demographic factors within states over time, and the effects of other related laws, results indicated substantial reductions in alcohol-positive involvement in fatal crashes were associated with the two youth-specific laws. The policy of limiting youth access to alcohol through MLDA laws and reinforcing this action by making it illegal for underage drivers to have any alcohol in their system appears to have been effective in reducing the proportion of fatal crashes involving drinking drivers.

This paper examines the correlates and predictors of driving under the influence behaviors (DUIBs) during the past month by college students. Measures of heavy episodic drinking, monthly drinking frequency, monthly drinking variance, monthly drinks per occasion and reported marijuana use are compared as predictors net of other predictive factors. A cross-sectional telephone survey was conducted with college students by a university social science research laboratory. Respondents attended two large public universities located in the southwestern part of the US. Participants included 803 randomly selected college students. The interview schedule included items from the Core Alcohol and Drug Survey and the College Alcohol Risk Assessment Guide. Several additional last-drinking-event items were also developed for the interview. Bivariate analyses indicate that marijuana use (past year), heavy episodic drinking, reports of DUIBs (driving under the influence or riding with a driver who is under the influence) in the past year, monthly frequency of drinking, the average number of drinks consumed when drinking and age are correlates of DUIBs during the past month. Multivariate analyses indicate past year DUIBs, monthly frequency of drinking and monthly marijuana use predicted recent DUIB.

License suspension effectively reduces recidivism and crash involvement of those convicted of driving while impaired (DWI). The impact of this sanction, however, is being reduced by the large number of offenders (up to 75%) who drive even though suspended. To deal with this problem. several states have enacted laws providing for vehicle impoundment, immobilization, or forfeiture for repeat DWI offenders and for driving while suspended (DWS) offenders. Although a 1992 review of vehicle sanctions for DWI and DWS offenders showed 32 states with such laws, they were infrequently applied. Further, none of those laws had been adequately evaluated. This paper reviews the studies of vehicle action programs in California, Minnesota, New York, Ohio, Oregon, and Washington that have been applied broadly enough to permit evaluation. Although none of the studies has applied random assignment to ensure equal groups. several have applied sufficient statistical controls to provide reasonably credible results. All the programs reviewed showed positive effects. including some relatively large recidivism reductions, from denying offenders the use of their vehicles for 1-6 months. Highlighted in this review are several issues that appear to be important to the effectiveness of vehicle sanctioning programs.

This paper presents an analysis of the relationships between the passage of key alcohol safety laws and the number of drinking drivers in fatal crashes. The study evaluated three major alcohol safety laws--administrative license revocation laws, 0.10 illegal per se, and 0.08 illegal per se laws--on the proportion of drinking drivers in fatal crashes. Drivers aged 21 and older in fatal crashes at two BAC levels--0.01-0.09 and 0.10 or greater--were considered separately. Drivers under age 21 were not included because they are affected by the Minimum Legal Drinking Age (MLDA) law. This study used data on drinking drivers in fatal crashes from the Fatality Analysis Reporting System (FARS) covering 16 years (1982-1997) for all 50 states and the District of Columbia. Also included in the study were such variables as per capita alcohol consumption and annual vehicle miles traveled (VMT), which could affect the number of alcohol-related crashes. The results indicate that each of the three laws had a significant relationship to the downward trend in alcohol-related fatal crashes in the United States over that period. This paper points out that this long-term trend is not the product of a single law. Instead, it is the result of the growing impact of several laws over time plus the affect of some factors not included in the model tested (such as the increasing use of sobriety checkpoints and the media's attention to the drinking-and-driving problem).

This analysis examines whether roadside surveys that measure changes in the prevalence of driving after drinking can be used to evaluate the impact of interventions designed to reduce alcohol-related traffic crashes. Using data collected at a roadside survey over a 4-year period in two California communities (N = 33,614), this analysis examines the relationship of BAC and drinks since 5 P.M., aggregated on a monthly basis, with nighttime injury crash data from the California Highway Patrol aggregated on a monthly basis. A regression analysis was used in which daytime injury and drinking style were covariates. The data demonstrate that temporal changes in drinking and driving collected at a roadside survey reflect temporal changes in nighttime injury rates. Hence, this study substantiates the use of roadside surveys as an appropriate methodology to evaluate drinking and driving interventions.

This report covers an evaluation of programs designed to reduce unlawful driving in the states of Washington and Oregon by providing for the marking of the license plate of a vehicle when its operator was apprehended driving while suspended. In both states, the records of 101,000 drivers convicted of a drunk-driving offense who were potentially at risk for this sanction were analyzed using time series analysis to determine the general deterrent effect of the law. In addition, the specific deterrent effect of having one's vehicle marked was studied in Oregon using analysis of covariance. Results of these analyses indicated that the law had both a general and specific deterrence effect in Oregon but no measurable effect in Washington.

Driving while suspended is a growing problem in most states. To deal with this problem, a number of jurisdictions are impounding and/or immobilizing the vehicles of driving while suspended or multiple driving under the influence offenders. This study evaluates the first 2 years of the implementation of this type of law in Franklin County (Columbus), OH. Variations in police enforcement and judicial sentencing policies resulted in some offenders, though eligible for impoundment or immobilization, not receiving the sanction. The recidivism rates of these offenders were compared with offenders who did receive a vehicle sanction. Tracking these two groups of offenders for up to 2 years demonstrated that the offenders who received the sanction had lower recidivism rates, both before and after they reclaimed their vehicles.

This critique refutes Zador's claim [1976] that Alcohol Safety Action Projects, as large scale social programs have been ineffective. The discussion takes issue with Zador's comparison groups, statistical design, statistical methods, and use of 12-month fatality totals for data analysis. In addition to weaknesses and deficiencies in these areas, the authors find Zador's conclusion unfounded based on the analysis presented.

The effectiveness of drunk driving enforcement patrols is generally assumed. However, few adequate evaluations are available in the traffic safety literature. The U.S. Department of Transportation funded a special program in Stockton, a city with a population of 120,000 in the central valley of California, to test the effectiveness of special drunk driving patrols on weekend evenings, applied within a setting in which no other major alcohol safety programs were present. The objective of this effort was to determine the effectiveness of a "traditional" approach to enforcing driving while impaired (DWI) laws; one in which innovative procedures such as sobriety checkpoints were not used. The results indicated that nighttime collisions in Stockton were reduced during the three and a half year period of the special enforcement program.