Seasonal and Time-Trend Variation by Gender of Alcohol-Impaired Drivers at Preventive Sobriety Checkpoints.

OBJECTIVE: We aimed to analyze the evolution over time and the seasonality of outcomes of nonrandom alcohol concentration breath tests performed on drivers at sobriety checkpoints in Catalonia (Spain) from 2005 to 2012. Differences by gender are also explored. METHOD: This study was a time-series analysis of the monthly prevalence of drunk drivers by gender. The sample consisted of all drivers tested at nonrandom sobriety checkpoints in Catalonia (N = 3,985,000). Our outcome variable was the monthly prevalence of drivers with a breath alcohol concentration at or above the legal limit. The driver's gender was also registered. RESULTS: A decreasing trend in alcohol-impaired driving over time was found. The gender gap diminished after 2008 and disappeared in 2012. After adjusting for the trend, the lowest monthly coefficient for men was recorded in January (3.91, p < .001) and the highest in July (4.72, p < .001) and September (4.75, p < .001). The lowest monthly coefficient for women was also recorded in January (3.05, p < .001) but the highest in October (4.12, p < .001). After seasonal aggregation, the lowest coefficient was recorded in winter for both men and women, whereas a peak was found for men in spring and for women in autumn. CONCLUSIONS: Seasonal patterns for male and female drivers testing positive at nonrandom sobriety checkpoints indicate that the prevalence of alcohol-impaired driving peaks in spring for males and in autumn for females. We recommend that the authorities enforce campaigns that target male and female drinkers accordingly.

High Ambient Temperatures and Risk of Motor Vehicle Crashes in Catalonia, Spain (2000-2011): A Time-Series Analysis.

BACKGROUND: Experimental studies have shown a decrease in driving performance at high temperatures. The epidemiological evidence for the relationship between heat and motor vehicle crashes is not consistent. OBJECTIVES: We estimated the impact of high ambient temperatures on the daily number of motor vehicle crashes and, in particular, on crashes involving driver performance factors (namely distractions, driver error, fatigue, or sleepiness). METHODS: We performed a time-series analysis linking daily counts of motor vehicle crashes and daily temperature or occurrence of heat waves while controlling for temporal trends. All motor vehicle crashes with victims that occurred during the warm period of the years 2000-2011 in Catalonia (Spain) were included. Temperature data were obtained from 66 weather stations covering the region. Poisson regression models adjusted for precipitation, day of the week, month, year, and holiday periods were fitted to quantify the associations. RESULTS: The study included 118,489 motor vehicle crashes (an average of 64.1 per day). The estimated risk of crashes significantly increased by 2.9% [95% confidence interval (CI): 0.7%, 5.1%] during heat wave days, and this association was stronger (7.7%, 95% CI: 1.2%, 14.6%) when restricted to crashes with driver performance-associated factors. The estimated risk of crashes with driver performance factors significantly increased by 1.1% (95% CI: 0.1%, 2.1%) for each 1 °C increase in maximum temperature. CONCLUSIONS: Motor vehicle crashes involving driver performance-associated factors were increased in association with heat waves and increasing temperature. These findings are relevant for designing preventive plans in a context of global warming.

Prevalence of alcohol-impaired drivers based on random breath tests in a roadside survey in Catalonia (Spain).

Sobriety checkpoints are not usually randomly located by traffic authorities. As such, information provided by non-random alcohol tests cannot be used to infer the characteristics of the general driving population. In this paper a case study is presented in which the prevalence of alcohol-impaired driving is estimated for the general population of drivers. A stratified probabilistic sample was designed to represent vehicles circulating in non-urban areas of Catalonia (Spain), a region characterized by its complex transportation network and dense traffic around the metropolis of Barcelona. Random breath alcohol concentration tests were performed during spring 2012 on 7596 drivers. The estimated prevalence of alcohol-impaired drivers was 1.29%, which is roughly a third of the rate obtained in non-random tests. Higher rates were found on weekends (1.90% on Saturdays and 4.29% on Sundays) and especially at night. The rate is higher for men (1.45%) than for women (0.64%) and it shows an increasing pattern with age. In vehicles with two occupants, the proportion of alcohol-impaired drivers is estimated at 2.62%, but when the driver was alone the rate drops to 0.84%, which might reflect the socialization of drinking habits. The results are compared with outcomes in previous surveys, showing a decreasing trend in the prevalence of alcohol-impaired drivers over time.