Analysis of fatal motorcycle crashes: crash typing

There were 2074 crashes fatal to a motorcycle driver in the United States during 1992. A computer program was developed to convert Fatal Accident Reporting System (FARS) data for these crashes into standard format English language “crash reports.” The computer generated reports were analyzed and crash type categories were defined. Five defined crash type categories accounted for 1785 (86%) of the 2074 crash events: Ran off-road (41%); ran traffic control (18%); oncoming or head-on (11%); left-turn oncoming (8%); and motorcyclist down (7%). Alcohol and excessive speed were common factors associated with motorcyclist crash involvement. Left turns and failure to yield were common factors associated with the involvement of other motorists. Suggested countermeasures include helmet use and enforcement of speed and impaired driving laws.     

Examination of factors determining fault in two-vehicle motorcycle crashes

Motorcycle crashes frequently involve a combination of high-risk behaviors by the motorcyclist or the other crash-involved driver. Such behaviors may include riding or driving without appropriate licensure or while under the influence of alcohol, as well as deciding not to use a safety device such as a helmet or safety belt. Given that these factors frequently occur in combination with one another, it is difficult to untangle the specific effects of individual factors leading up to the crash outcome. This study assesses how various rider-, driver-, and other crash-specific factors contribute to at-fault status in two-vehicle motorcycle crashes, as well as how these same factors affect the propensity for other high-risk behaviors. Furthermore, the interrelationships among fault status and these other behaviors are also examined using a multivariate probit model. This model is developed using police-reported crash data for the years 2006–2010 from the State of Ohio. The results show that younger motorcyclists are more likely to be at-fault in the event of a collision, as are riders who are under the influence of alcohol, riding without insurance, or not wearing a helmet. Similarly, motorcyclists were less likely to be at-fault when the other driver was of younger age or was driving under the influence of alcohol, without insurance, or not wearing their safety belt. Crash-involved parties who engaged in one high-risk behavior were more likely to engage in other such behaviors, as well, and this finding was consistent for both motorcyclists and drivers. The results of this study suggest that educational and enforcement strategies aimed at addressing any one of these behaviors are likely to have tangential impacts on the other behaviors, as well.     

A longitudinal study of risk factors for motorcycle crashes among junior college students in Taiwan

A cohort of 4729 junior college students in an urban and a rural area in Taiwan was followed up for a period of 20 months. Students' characteristics, including riding exposures, as well as human, vehicular, and environmental factors were collected using one initial and three follow-up questionnaires. The Anderson-Gill (AG) multiplicative intensity model was used to determine the risk of a motorcycle crash over time while also allowing for the modeling of multiple events. The average response rate for the four assessments was 92%. The adjusted relative hazard (RH) for students living in the rural as opposed to the urban area for crashes was 1.67 at the beginning of the study but decreased to 0.66 by the end. Past motorcycle crash history, number of riding days, average riding distance, risk-taking level, alcohol consumption, and traffic violations were all significantly associated with an increased risk of being involved in a crash. Conversely, increasing age, riding experience, and automobile licensure were related to a decreased risk of crashing. Furthermore, helmet use was not independently related to the risk of crashing. In conclusion, a high-risk group predisposed to involvement in a motorcycle crash, including both non-injury and injury-related crashes, can be identified using selected risk factors for crash prevention among young riders.     

The effects of a new traffic safety law in the Republic of Serbia on driving under the influence of alcohol

The aim of the study presented here has been to see what the effects of the new traffic safety law are, 2 years into its initial implementation, on driving under the influence of alcohol. Until the end of 2009, the legal limit for blood concentration for drivers in Serbia was 0.5 g/l; however, the new traffic safety law stipulates the new limit to be 0.3 g/l. A retrospective autopsy study was performed over a 6-year period (from 2006 to 2011) whose sample covered cases of fatally injured drivers who had died at the scene of the incident, before being admitted to hospital. A total of 161 fatally injured drivers were examined for their blood alcohol concentration. The average age for these drivers was 40.2 ± 15.4 years, with a significant male predominance of 152 men to 9 women (χ² = 152.000, p < 0.001). This study has shown no decrease in the ratio of drivers under the influence of alcohol vs. all drivers (Pearson χ² = 4.415, df = 5, p = 0.491), nor in the number of drivers under the influence of alcohol (Pearson χ² = 6.629, df = 5, p = 0.250), nor a decrease in the mean blood alcohol concentration in drivers (1.72 ± 0.87 vs. 1.68 ± 0.95 g/l, t = 0.177, df = 80, p = 0.860). The conclusion of this study is that the new law has had a limited effect on driving under the influence of alcohol, which still remains one of the major human factors, responsible for road-traffic crashes in Serbia.     

Impairment of simulated motorcycle riding performance under low dose alcohol

Crash statistics that include the blood alcohol concentration (BAC) of vehicle operators reveal that crash involved motorcyclists are over represented at low BACs (e.g., ≤0.05%). This riding simulator study compared riding performance and hazard response under three low dose alcohol conditions (sober, 0.02% BAC, 0.05% BAC). Forty participants (20 novice, 20 experienced) completed simulated rides in urban and rural scenarios while responding to a safety-critical peripheral detection task (PDT). Results showed a significant increase in the standard deviation of lateral position in the urban scenario and PDT reaction time in the rural scenario under 0.05% BAC compared with zero alcohol. Participants were most likely to collide with an unexpected pedestrian in the urban scenario at 0.02% BAC, with novice participants at a greater relative risk than experienced riders. Novices chose to ride faster than experienced participants in the rural scenario regardless of BAC. Not all results were significant, emphasising the complex situation of the effects of low dose BAC on riding performance, which needs further research. The results of this simulator study provide some support for a legal BAC for motorcyclists below 0.05%.     

The role of experience and advanced training on performance in a motorcycle simulator

Motorcyclists are over-represented in collision statistics. While many collisions may be the direct fault of another road user, a considerable number of fatalities and injuries are due to the actions of the rider. While increased riding experience may improve skills, advanced training courses may be required to evoke the safest riding behaviours. The current research assessed the impact of experience and advanced training on rider behaviour using a motorcycle simulator. Novice riders, experienced riders and riders with advanced training traversed a virtual world through varying speed limits and roadways of different curvature. Speed and lane position were monitored. In a comparison of 60 mph and 40 mph zones, advanced riders rode more slowly in the 40 mph zones, and had greater variation in lane position than the other two groups. In the 60 mph zones, both advanced and experienced riders had greater lane variation than novices. Across the whole ride, novices tended to position themselves closer to the kerb. In a second analysis across four classifications of curvature (straight, slight, medium, tight) advanced and experienced riders varied their lateral position more so than novices, though advanced riders had greater variation in lane position than even experienced riders in some conditions. The results suggest that experience and advanced training lead to changes in behaviour compared to novice riders which can be interpreted as having a potentially positive impact on road safety.     

A dynamic analysis of motorcycle ownership and usage: A panel data modeling approach

This study aims to develop motorcycle ownership and usage models with consideration of the state dependence and heterogeneity effects based on a large-scale questionnaire panel survey on vehicle owners. To account for the independence among alternatives and heterogeneity among individuals, the modeling structure of motorcycle ownership adopts disaggregate choice models considering the multinomial, nested, and mixed logit formulations. Three types of panel data regression models – ordinary, fixed, and random effects – are developed and compared for motorcycle usage. The estimation results show that motorcycle ownership in the previous year does exercise a significantly positive effect on the number of motorcycles owned by households in the current year, suggesting that the state dependence effect does exist in motorcycle ownership decisions. In addition, the fixed effects model is the preferred specification for modeling motorcycle usage, indicating strong evidence for existence of heterogeneity. Among various management strategies evaluated under different scenarios, increasing gas prices and parking fees will lead to larger reductions in total kilometers traveled.     

Retail alcohol monopolies, underage drinking, and youth impaired driving deaths

OBJECTIVE: To explore associations of state retail alcohol monopolies with underage drinking and alcohol-impaired driving deaths. DATA: Surveys on youth who drank alcohol and binge-drank recently and their beverage choices; census of motor vehicle fatalities by driver blood alcohol level. METHODS: Regressions estimated associations of monopolies with under-21 drinking, binge drinking, alcohol-impaired driving deaths, and odds a driver under 21 who died was alcohol-positive. RESULTS: About 93.8% of those ages 12-20 who consumed alcohol in the past month drank some wine or spirits. In states with a retail monopoly over spirits or wine and spirits, an average of 14.5% fewer high school students reported drinking alcohol in the past 30 days and 16.7% fewer reported binge drinking in the past 30 days than high school students in non-monopoly states. Monopolies over both wine and spirits were associated with larger consumption reductions than monopolies over spirits only. Lower consumption rates in monopoly states, in turn, were associated with a 9.3% lower alcohol-impaired driving death rate under age 21 in monopoly states versus non-monopoly states. Alcohol monopolies may prevent 45 impaired driving deaths annually. CONCLUSIONS: Continuing existing retail alcohol monopolies should help control underage drinking and associated harms.     

Effects of alcohol impairment on motorcycle riding skills

Alcohol intoxication is a significant risk factor for fatal traffic crashes; however, there is sparse research on the impairing effects of alcohol on skills involved in motorcycle control. Twenty-four male motorcycle riders between the ages of 21 and 50 were assessed on a test track with task scenarios based on the Motorcycle Safety Foundation's (MSF) training program. A balanced incomplete block design was used to remove confounding artifacts (learning effects) by randomizing four BAC levels across three test days. In general, intoxicated riders demonstrated longer response times and adopted larger tolerances leading to more task performance errors. Most of the alcohol effects were evident at the per se 0.08% alcohol level, but some of the effects were observed at the lower 0.05% alcohol level. The effects of alcohol on motorcycle control and rider behavior were modest and occurred when task demand was high (offset weave), time pressure was high (hazard avoidance for near obstacles), and tolerances were constrained (circuit track). The modest effects may be due to the study design, in which experienced riders performed highly practiced, low-speed tasks; alcohol at these levels may produce larger effects with less experienced riders in more challenging situations.     

The role of parental alcohol consumption on driving under the influence of alcohol: results from a longitudinal, nationally representative sample

Purpose

Many studies have examined the role of peer and parental alcohol use on drinking behaviors among adolescents. Few studies, however, have examined parental influences on driving under the influence (DUI) of alcohol. The current study uses data from a longitudinal study to examine the role of parental alcohol use during adolescence on the risk for DUI among young adult men and women.

Methods

Data were derived from 9559 adolescents and young adults who participated in the National Longitudinal Study of Adolescent Health (Add Health) Waves I and III. Survey logistic regression was used to examine the relationship between multilevel risk and protective factors and self-reported DUI. Analyses were stratified by gender and frequency of parental alcohol consumption to understand the role of parental alcohol use on risk for DUI among their youth.

Results

Risk and protective factors for DUI were very similar among men and women. Parental alcohol use significantly predicted DUI among women (OR = 1.39, p < 0.01) and men (OR = 1.33, p < 0.05). When parents did not report alcohol use, peer alcohol use significantly increased risk for DUI for both women (OR = 1.26, p < 0.05) and men (OR = 1.31, p < 0.001). When parents reported alcohol use, however, peer alcohol use was not a significant independent predictor.

Conclusions

Findings suggest remarkable similarities in risk and protective factors for DUI across gender groups. For men and women, parental alcohol consumption was a risk factor for DUI. Peers’ alcohol use predicted DUI only when parents did not use alcohol.     

Effects of lowering the legal BAC to 0.08 on single-vehicle-nighttime fatal traffic crashes in 19 jurisdictions

Background: In the past few decades, numerous policies, including those that lower legal blood alcohol concentration limits, have been enacted to reduce alcohol-impaired driving. In the US, 41 states and the District of Columbia have enacted 0.08 per se laws, which specify that if a driver’s BAC is at or above 0.08, a violation has occurred even if the driver does not show signs of intoxication. Objective: We examined effects of lowering the blood alcohol concentration limit to 0.08 per se on fatal traffic crashes in 18 states and the District of Columbia, and whether effects of the law varied by state or by baseline rates of fatal traffic crashes. Method: Data on fatal traffic crashes were obtained from the Fatality Analysis Reporting System, including all states that enacted 0.08 per se prior to 2001 in the contiguous United States. Effects of the 0.08 law were examined in each state separately, and the overall effect across states was examined using a mixed-model Poisson regression on single-vehicle-nighttime fatal traffic crashes. Results: State-specific analyses showed that fatal traffic crashes significantly decreased in three of the 19 states following the introduction of the 0.08 law, prior to adjusting for potential confounders. The mixed-model regression showed a statistically significant 5.2% reduction in single-vehicle-nighttime fatal traffic crashes associated with the 0.08 law across all states, after adjusting for administrative license revocation, the number of Friday and Saturday nights in a month, and trends in all other types of fatal traffic crashes. Findings indicate that the effect of the 0.08 law does not vary significantly by state or baseline rate of fatal traffic crashes in a state, and no significant statistical interaction exists between 0.08 and administrative license revocation policy effects.     

Driving under the influence of alcohol: Examining ethno-specific rates and the mediating effects of psychological distress and harmful and problematic drinking

This paper examines ethnic disparities in rates of driving under the influence of alcohol (DUIA) in a representative sample of Ontario adults. Data were drawn from the Centre for Addiction and Mental Health (CAMH) Monitor, a survey of 8276 Ontario adults aged 18 and older. We considered 19 distinct ethnic groups based on participants’ self-identification of ethno-cultural heritage. Differences in the prevalence of DUIA across ethnic groups were limited. Relative to other ethnic groups, those adults who identified as Irish had a significantly higher rate of DUIA, while those of Italian and Chinese ethnicity had significantly lower rates of DUIA. The mediating effects of psychological distress (General Health Questionnaire) and harmful and problematic drinking (Alcohol Use Disorders Identification Test [AUDIT] consumption, dependence and problems) on the direct relationship between ethnic identity and impaired driving were also considered. Mediation was observed as remaining ethnic differences in DUIA disappeared when AUDIT subscales were introduced. These findings are interpreted in the context of patterns of alcohol consumption among ethnic populations and their impact on DUIA. Implications of study findings are considered with respect to the role of ethnicity in impaired driving research and its impact on programs and policies directed at reducing impaired driving.     

Novice riders and the predictors of riding without motorcycle protective clothing

Background

While helmet usage is often mandated, few motorcycle and scooter riders make full use of protection for the rest of the body. Little is known about the factors associated with riders’ usage or non-usage of protective clothing.

Methods

Novice riders were surveyed prior to their provisional licence test in NSW, Australia. Questions related to usage and beliefs about protective clothing, riding experience and exposure, risk taking and demographic details. Multivariable Poisson regression models were used to identify factors associated with two measures of usage, comparing those who sometimes vs rarely/never rode unprotected and who usually wore non-motorcycle pants vs motorcycle pants.

Results

Ninety-four percent of eligible riders participated and usable data was obtained from 66% (n = 776). Factors significantly associated with riding unprotected were: youth (17–25 years) (RR = 2.00, 95% CI: 1.50–2.65), not seeking protective clothing information (RR = 1.29, 95% CI = 1.07–1.56), non-usage in hot weather (RR = 3.01, 95% CI: 2.38–3.82), awareness of social pressure to wear more protection (RR = 1.48, 95% CI: 1.12–1.95), scepticism about protective benefits (RR = 2.00, 95% CI: 1.22–3.28) and riding a scooter vs any type of motorcycle. A similar cluster of factors including youth (RR = 1.17, 95% CI: 1.04–1.32), social pressure (RR = 1.32, 95% CI: 1.16–1.50), hot weather (RR = 1.30, 95% CI: 1.19–1.41) and scooter vs motorcycles were also associated with wearing non-motorcycle pants. There was no evidence of an association between use of protective clothing and other indicators of risk taking behaviour.

Conclusions

Factors strongly associated with non-use of protective clothing include not having sought information about protective clothing and not believing in its injury reduction value. Interventions to increase use may therefore need to focus on development of credible information sources about crash risk and the benefits of protective clothing. Further work is required to develop motorcycle protective clothing suitable for hot climates.     

A review of risk factors and patterns of motorcycle injuries

Per vehicle mile traveled, motorcycle riders have a 34-fold higher risk of death in a crash than people driving other types of motor vehicles. While lower-extremity injuries most commonly occur in all motorcycle crashes, head injuries are most frequent in fatal crashes. Helmets and helmet use laws have been shown to be effective in reducing head injuries and deaths from motorcycle crashes. Alcohol is the major contributing factor to fatal crashes. Enforcement of legal limits on the blood alcohol concentration is effective in reducing motorcycle deaths, while some alcohol-related interventions such as a minimal legal drinking age, increased alcohol excise taxes, and responsible beverage service specifically for motorcycle riders have not been examined. Other modifiable protective or risk factors comprise inexperience and driver training, conspicuity and daytime headlight laws, motorcycle licensure and ownership, riding speed, and risk-taking behaviors. Features of motorcycle use and potentially effective prevention programs for motorcycle crash injuries in developing countries are discussed. Finally, recommendations for future motorcycle-injury research are made.     

Predicting road crashes from a mathematical model of alertness regulation--The Sleep/Wake Predictor

Sleepiness is related to factors such as the time of day, the time since awakening and the duration of prior sleep. The present study investigated whether actual road crashes could be predicted from a mathematical model based on these three factors (the Sleep/Wake Predictor-SWP). Data were derived from a population-based case-control study of serious injury crashes. Data on accident time (or control sampling time) and start and end of prior sleep were entered into the model (blind). The predicted sleepiness values were used in logistic regressions. The results showed a highly significant odds ratio (OR)=1.72 (confidence interval=1.41-2.09) for each incremental step of sleepiness on the output sleepiness scale (nine steps). There was also a significant interaction with blood alcohol level, showing high OR values for high sleepiness levels and alcohol levels above 50 mg% (0.05 g/dl). It was concluded that the model is a good predictor of road crashes beyond that of alcohol level, and that interaction between the two carries a very high risk.     

Drug use among drivers who drank on alcohol outlets from Porto Alegre,Brazil

Background

Driving under the influence of multiple substances is a public health concern, but there is little epidemiological data about their combined use and putative impact on driving in low and middle-income countries where traffic crashes have been clustering in recent years. The aim of this study is to estimate the prevalence of alcohol and drug use – as well as their associated factors – among drivers in the context of alcohol outlets (AOs).

Methods

A probability three-stage sample survey was conducted in Porto Alegre, Brazil. Individuals who were leaving AO were screened, with the selection of 683 drivers who met the inclusion criteria. Drivers answered a structured interview, were breathalyzed, and had their saliva collected for drug screening. Prevalences were assessed using domain estimation and logistic regression models assessed covariates associated with substance use.

Findings

Benzodiazepines 3.9% (SE 2.13) and cocaine 3.8% (SE 1.3) were the most frequently detected drugs in saliva. Among drivers who were going to drive, 11% had at least one drug identified by the saliva drug screening, 0.4% two, and 0.1% three drugs in addition to alcohol. In multivariable analyses, having a blood alcohol concentration (BAC) > 0.06% was found to be associated with a 3.64 times (CI 95% 1.79–7.39) higher chance of drug detection, compared with interviewees with lower BACs.

Conclusions

To drive under the influence of multiple substances is likely to be found in this setting, highlighting an association between harmful patterns of consume of alcohol and the misuse of other substances.     

Prevalence of teen driver errors leading to serious motor vehicle crashes

Objectives

Motor vehicle crashes are the leading cause of adolescent deaths. Programs and policies should target the most common and modifiable reasons for crashes. We estimated the frequency of critical reasons for crashes involving teen drivers, and examined in more depth specific teen driver errors.

Methods

The National Highway Traffic Safety Administration's (NHTSA) National Motor Vehicle Crash Causation Survey collected data at the scene of a nationally representative sample of 5470 serious crashes between 7/05 and 12/07. NHTSA researchers assigned a single driver, vehicle, or environmental factor as the critical reason for the event immediately leading to each crash. We analyzed crashes involving 15–18 year old drivers.

Results

822 teen drivers were involved in 795 serious crashes, representing 335,667 teens in 325,291 crashes. Driver error was by far the most common reason for crashes (95.6%), as opposed to vehicle or environmental factors. Among crashes with a driver error, a teen made the error 79.3% of the time (75.8% of all teen-involved crashes). Recognition errors (e.g., inadequate surveillance, distraction) accounted for 46.3% of all teen errors, followed by decision errors (e.g., following too closely, too fast for conditions) (40.1%) and performance errors (e.g., loss of control) (8.0%). Inadequate surveillance, driving too fast for conditions, and distracted driving together accounted for almost half of all crashes. Aggressive driving behavior, drowsy driving, and physical impairments were less commonly cited as critical reasons. Males and females had similar proportions of broadly classified errors, although females were specifically more likely to make inadequate surveillance errors.

Conclusions

Our findings support prioritization of interventions targeting driver distraction and surveillance and hazard awareness training.     

Acceptance of drinking and driving and alcohol-involved driving crashes in California

BackgroundAlcohol-impaired driving accounts for substantial proportion of traffic-related fatalities in the U.S. Risk perceptions for drinking and driving have been associated with various measures of drinking and driving behavior. In an effort to understand how to intervene and to better understand how risk perceptions may be shaped, this study explored whether an objective environmental-level measure (proportion of alcohol-involved driving crashes in one’s residential city) were related to individual-level perceptions and behavior.MethodsUsing data from a 2012 cross-sectional roadside survey of 1147 weekend nighttime drivers in California, individual-level self-reported acceptance of drinking and driving and past-year drinking and driving were merged with traffic crash data using respondent ZIP codes. Population average logistic regression modeling was conducted for the odds of acceptance of drinking and driving and self-reported, past-year drinking and driving.ResultsA non-linear relationship between city-level alcohol-involved traffic crashes and individual-level acceptance of drinking and driving was found. Acceptance of drinking and driving did not mediate the relationship between the proportion of alcohol-involved traffic crashes and self-reported drinking and driving behavior. However, it was directly related to behavior among those most likely to drink outside the home.DiscussionThe present study surveys a particularly relevant population and is one of few drinking and driving studies to evaluate the relationship between an objective environmental-level crash risk measure and individual-level risk perceptions. In communities with both low and high proportions of alcohol-involved traffic crashes there was low acceptance of drinking and driving. This may mean that in communities with low proportions of crashes, citizens have less permissive norms around drinking and driving, whereas in communities with a high proportion of crashes, the incidence of these crashes may serve as an environmental cue which informs drinking and driving perceptions. Perceptual information on traffic safety can be used to identify places where people may be at greater risk for drinking and driving. Community-level traffic fatalities may be a salient cue for tailoring risk communication.     

The contribution of alcohol to night time crash risk and other risks of night driving

Many studies show that driving at night is more risky in terms of crash involvements per distance travelled than driving during the day. The reasons for this include the more prevalent use of alcohol by drivers at night, the effects of fatigue on the driving task and the risk associated with reduced visibility. Although the consumption of alcohol prior to driving occurs most commonly at night, drink-driving is not inherently a night time risk factor. This study decomposes the New Zealand risk of driving at night into risk associated with alcohol and risk associated with inherently night time factors. The overall risk associated with alcohol use by drivers was shown to decrease with increasing age for the most risky situation analysed (male drivers on weekend nights). Given the levels of drinking and driving on weekend nights, the overall effect of alcohol was shown to contribute almost half of weekend night time risk for drivers aged under 40 on lower volume roads, but to contribute little to overall risk on higher-volume roads, consistent with other research showing that higher-volume roads are not favoured by drinking drivers. Risk at night relative to risk during the day (excluding risk associated with drinking and driving) was shown to decrease with age. Roads with illumination at night are less risky at night relative to during the day than roads without illumination. The risks estimated in this paper reflect the behaviour of the road users studied and their prevalence on the roads under the conditions analysed.     

Alcohol-impaired driving behavior and sensation-seeking disposition in a college population receiving routine care at campus health services centers

Accidents stemming from alcohol-impaired driving are the leading cause of injury and death among college students. Research has implicated certain driver personality characteristics in the majority of these motor vehicle crashes. Sensation seeking in particular has been linked to risky driving, alcohol consumption, and driving while intoxicated. This study investigated the effect of sensation seeking on self-reported alcohol-impaired driving behavior in a college student population while adjusting for demographics, residence and drinking locations. A total of 1587 college students over the age of 18 completed a health screening survey while presenting for routine, non-urgent care at campus heath services centers. Student demographics, living situation, most common drinking location, heavy episodic drinking, sensation-seeking disposition and alcohol-impaired driving behavior were assessed. Using a full-form logistic regression model to isolate sensation seeking after adjusting for covariates, sensation seeking remains a statistically significant independent predictor of alcohol-impaired driving behavior (OR = 1.52; CI = 1.19-1.94; p < 0.001). Older, white, sensation-seeking college students who engage in heavy episodic drinking, live off-campus, and go to bars are at highest risk for alcohol-impaired driving behaviors. Interventions should target sensation seekers and environmental factors that mediate the link between sensation seeking and alcohol-impaired driving behaviors.