Traffic environment and demographic factors affecting impaired driving and crashes

IntroductionData availability has forced researchers to examine separately the role of alcohol among drivers who crashed and drivers who did not crash. Such a separation fails to account fully for the transition from impaired driving to an alcohol-related crash.MethodIn this study, we analyzed recent data to investigate how traffic-related environments, conditions, and drivers’ demographics shape the likelihood of a driver being either involved in a crash (alcohol impaired or not) or not involved in a crash (alcohol impaired or not). Our data, from a recent case–control study, included a comprehensive sampling of the drivers in nonfatal crashes and a matched set of comparison drivers in two U.S. locations. Multinomial logistic regression was applied to investigate the likelihood that a driver would crash or would not crash, either with a blood alcohol concentration (BAC) = .00 or with a BAC ≥ .05.ConclusionsTo our knowledge, this study is the first to examine how different driver characteristics and environmental factors simultaneously contribute to alcohol use by crash-involved and non-crash-involved drivers. This effort calls attention to the need for research on the simultaneous roles played by all the factors that may contribute to motor vehicle crashes.     

Tracking progress in teenage driver crash risk in the United States since the advent of graduated driver licensing programs

IntroductionThis study examined U.S. teenagers' crash rates since 1996, when the first graduated driver licensing (GDL) program in the United State was implemented.MethodsPassenger vehicle driver crash involvement rates for 16–19 and 30–59 (middle-aged) year-olds were examined, using data from the Fatality Analysis Reporting System, National Automotive Sampling System General Estimates System, Census Bureau, and National Household Travel Surveys.ResultsPer capita fatal and police-reported crash rates in 2012 were lower for 16 year-olds than for middle-aged drivers but older teenagers' rates were higher. Mileage-based fatal and police-reported crash rates in 2008 were higher for teenagers than for middle-aged drivers and higher for 16–17 year-olds than for older teenagers. In 1996–2012, teenagers' per capita fatal and police-reported crash rates declined sharply, especially for 16–17 year-olds, and more so than for middle-aged drivers. Substantial declines also occurred in teenagers' mileage-based fatal and police-reported crash rates from 1995–96 to 2008, generally more so than for middle-aged drivers. Regarding factors in fatal crashes in 1996 and 2012, proportions of young teenagers' crashes occurring at night and with multiple teenage passengers declined, more so than among older teenagers and middle-aged drivers. The proportion of fatally injured drivers who had been drinking declined for teenagers but changed little for middle-aged drivers. Improvements were not apparent in rates of driver errors or speeding among teenage drivers in fatal crashes.ConclusionsTeenage drivers' crash risk dropped during the period of implementation of GDL laws, especially fatal crash types targeted by GDL. However, teenagers' crash risk remains high, and important crash factors remain unaddressed by GDL.Practical applicationsAlthough this study was not designed to examine the role of GDL, the results are consistent with the increased presence of such laws. More gains are achievable if states strengthen their laws.     

Healthcare utilization and costs among older adult female drivers and former drivers

PurposeThis study compared the healthcare utilization and costs for specific types of medical services among older adult women who currently drive and those who no longer drive.MethodsThis study included 347 women aged 65 or older who were either former (had stopped driving) or current drivers, randomly sampled from a large U.S. health plan to participate in a telephone survey, and who had automated health records with healthcare utilization and cost data. Bivariate analyses and generalized linear modeling were used to examine associations between driving status and healthcare utilization and costs.ResultsAdjusting for age, income, and marital status, former drivers were more likely than current drivers to use mental health care services (RR = 3.37; 95% CI: 1.03, 10.98). Former drivers also tended to use more inpatient (RR = 1.85; 95% CI: 0.88, 3.87) and emergency services (RR = 1.89; 95% CI: 0.96, 3.70), but results did not reach statistical significance. Total annual healthcare costs in 2005 were almost twice as high for former drivers compared with current drivers ($13,046 vs. $7,054; mean difference = $5,992; 95% CI: -$360, $12,344), although this relationship was not statistically significant (CR = 1.61; 95% CI: 0.88, 2.96).Impact on IndustryFormer drivers were more than three times as likely as current drivers to use mental health services, and tended to use more emergency and inpatient services. Further research on factors that potentially mediate the relationship between driving status and health service use is warranted.     

Distracting behaviors among teenagers and young,middle-aged,and older adult drivers when driving without and with warnings from an integrated vehicle safety system

IntroductionNegative reinforcement from crash warnings may reduce the likelihood that drivers engage in distracted driving. Alternatively, drivers may compensate for the perceived safety benefit of crash warnings by engaging in distractions more frequently, especially at higher speeds. The purpose of this study was to examine whether warning feedback from an integrated vehicle-based safety system affected the likelihood that various secondary behaviors were present among drivers ages 16–17, 20–30, 40–50, and 60–70.MethodParticipants drove an instrumented sedan with various collision warning systems for an extended period. Ten 5-second video clips were randomly sampled from driving periods at speeds above 25 mph and below 5 mph each week for each driver and coded for the presence of 11 secondary behaviors.ResultsAt least one secondary behavior was present in 46% of video clips; conversing with a passenger (17%), personal grooming (9%), and cellphone conversation (6%) were the most common. The likelihood that at least one secondary behavior was present was not significantly different during periods when drivers received warnings relative to periods without warnings. At least one secondary behavior was 21% more likely to be present at speeds below 5 mph relative to speeds above 25 mph; however, the effect of vehicle speed was not significantly affected by warning presence. Separate models for each of the five most common secondary behaviors also indicated that warnings had no significant effect on the likelihood that each behavior was present.ConclusionsCollision warnings were not associated with significant increases or decreases in the overall likelihood that teen and adult drivers engaged in secondary behaviors or the likelihood of the behaviors at speeds above 25 mph or below 5 mph.Practical applicationsThere was no evidence that forward collision warning and other technologies like those in this study will increase or decrease distracted driving.     

Driver speed selection and crash risk: Insights from the naturalistic driving study

IntroductionThis study investigates how speed limits affect driver speed selection, as well as the related crash risk, while controlling for various confounding factors such as traffic volumes and roadway geometry. Data from a naturalistic driving study are used to examine how driver speed selection varies among freeways with different posted speed limits, as well as how the likelihood of crash/near-crash events change with respect to mean speed and standard deviation.MethodRegression models are estimated to assess three measures of interest: the average speed of vehicles during the time preceding crash/near-crash and baseline (i.e., normal) driving events; the variation in travel speeds leading up to each event as quantified by the standard deviation in speeds over this period; and the probability of a specific event resulting in a crash/near-crash based on speed selection and other factors.ResultsSpeeds were relatively stable across levels-of-service A and B, within a range of 1.5 mph on average. Speeds were marginally lower (3.3 mph) on freeways posted at 65 mph versus 70 mph. In comparison, speeds were approximately 10.2 to 13.4 mph lower on facilities posted at 55 mph or 60 mph. Speeds were shown to be 2.5 mph lower in rainy weather and 11 mph lower under snow or sleet.ConclusionsSignificant correlation was observed with respect to speed selection behavior among the same individuals. Mean speeds are shown to increase with speed limits. However, these increases are less pronounced at higher speed limits. Drivers tend to reduce their travel speeds in presence of junctions and work zones, under adverse weather conditions, and particularly under heavy congestion. Crash risk increased with the standard deviation in speed, as well as on vertical curves and ramp junctions, and among the youngest and oldest age groups of drivers.     

Examining teen driver crashes and the prevalence of distraction: Recent trends, 2007–2015

IntroductionTeen drivers crash at a much higher rate than adult drivers, with distractions found as a factor in nearly 6 out of 10 moderate-to-severe teen crashes. As the driving environment continues to rapidly evolve, it is important to examine the effect these changes may be having on our youngest and most vulnerable drivers.MethodThe purpose of this study was to identify types of vehicle crashes teens are most frequently involved in, as well as the distracting activities being engaged in leading up to these crashes, with a focus on identifying changes or trends over time. We examined 2,229 naturalistic driving videos involving drivers ages 16–19. These videos captured crashes occurring between 2007 and 2015. The data of interest for this study included crash type, behaviors drivers engaged in leading up to the collision, total duration of time the driver's eyes were off the forward roadway, and duration of the longest glance away from forward.ResultsRear-end crashes increased significantly (annual % change = 3.23 [2.40–4.05]), corresponding with national data trends. Among cell phone related crashes, a significant shift occurred, from talking/listening to operating/looking (annual % change = 4.22 [1.15–7.29]). Among rear-end crashes, there was an increase in the time drivers' eyes were off the road (β = 0.1527, P = 0.0004) and durations of longest glances away (β = 0.1020, P = 0.0014).ConclusionsFindings suggest that shifts in the way cell phones are being used, from talking/listening to operating/looking, may be a cause of the increasing number of rear-end crashes for teen drivers.Practical applicationsUnderstanding the role that cell phone use plays in teen driver crashes is extremely important. Knowing how and when teens are engaging in this behavior is the only way effective technologies can be developed for mitigating these crashes.     

How do older adult drivers self-regulate? Characteristics of self-regulation classes defined by latent class analysis

ProblemMotor-vehicle crashes were the second leading cause of injury death for adults aged 65–84 years in 2014. Some older drivers choose to self-regulate their driving to maintain mobility while reducing driving risk, yet the process remains poorly understood.MethodsData from 729 older adults (aged ≥ 60 years) who joined an older adult ride service program between April 1, 2010 and November 8, 2013 were analyzed to define and describe classes of driving self-regulation. Latent class analysis was employed to characterize older adult driving self-regulation classes using driving frequency and avoidance of seven driving situations. Logistic regression was used to explore associations between characteristics affecting mobility and self-regulation class.ResultsThree classes were identified (low, medium, and high self-regulation). High self-regulating participants reported the highest proportion of always avoiding seven risky driving situations and the lowest driving frequency followed by medium and low self-regulators. Those who were female, aged 80 years or older, visually impaired, assistive device users, and those with special health needs were more likely to be high self-regulating compared with low self-regulating.Conclusions and practical applicationsAvoidance of certain driving situations and weekly driving frequency are valid indicators for describing driving self-regulation classes in older adults. Understanding the unique characteristics and mobility limitations of each class can guide optimal transportation strategies for older adults.     

Young drivers' perceptions of culpability of sleep-deprived versus drinking drivers

Introduction: Sleep-deprived driving can be as dangerous as alcohol-impaired driving, however, little is known about attitudes toward sleep-deprived drivers. This study examined the extent to which young drivers regard sleep-deprived compared to drinking drivers as culpable for a crash, and how their perceptions of driving while in these conditions differ. Method: University student participants (N = 295; M = 20.4 years, SD = 1.3; 81% women) were randomly assigned to read one of five fatal motor-vehicle crash scenarios, which differed by aspects of the driver's condition. Culpability ratings for the drinking driver were higher than those for the sleep-deprived driver. Results: Qualitative findings revealed that driving while sleep-deprived was viewed as understandable, and driving after drinking was viewed as definitely wrong. The dangers of sleep-deprived driving remain under-recognized.     

School transportation mode,by distance between home and school,United States,ConsumerStyles 2012

IntroductionMotor-vehicle crashes are a leading cause of death among children in the United States, and almost one-fourth of all trips by school-aged children are trips to and from school. This study sought to determine how children (5–18 years) travel to and from school and, among those living ≤ 1 mile of school, to explore the role of school bus service eligibility on school travel mode.MethodsWe used national 2012 survey data to determine prevalence of usual school travel mode, stratified by distance from school. For those living ≤ 1 mile of school, multivariable regression was conducted to assess the association between bus service eligibility and walking or bicycling.ResultsAlmost half (46.6%) of all children rode in passenger vehicles (PV) to school and 41.8% did so for the trip home. Results were similar among those living ≤ 1 mile (48.1%, PV to school; 41.3%, PV to home). Among those living ≤ 1 mile, 21.9% and 28.4% of children walked or bicycled to and from school, respectively. Ineligibility for school bus service was strongly associated with walking or bicycling to school [adjusted prevalence ratio (aPR: 5.36; p < 0.001)] and from school (aPR: 5.36; p < 0.001).ConclusionsRegardless of distance from school, passenger vehicles were a common mode of travel. For children who live close to school, the role that school bus service eligibility plays in walking or bicycling deserves further consideration.Practical applicationsGiven the large proportion of children who use passenger vehicles for school travel, effective interventions can be adopted to increase proper child restraint and seat belt use and reduce crash risks among teen drivers. Better understanding of conditions under which bus service is offered to children who live close to school could inform efforts to improve pedestrian and bicyclist safety for school travel.     

Older drivers’ involvement in fatal RTCs. Do crashes fatal to them differ from crashes involving them but fatal to others?

In several countries, older drivers are disproportionately involved in fatal road traffic crashes (RTCs) for various reasons. This study maps the circumstances of occurrence of crashes involving older drivers that are fatal to either them or other road users and highlights differences between them. Sweden’s national in-depth studies of fatal RTCs archive was used and focus was placed on crashes in which a driver aged 65 years or older was involved between 2002 and 2004 (n = 197). Thirteen driver and crash characteristics were analyzed simultaneously and typical crash patterns (classes) were highlighted. For each pattern, the proportions of crashes fatal to the older driver vs. to someone else were compared. Four patterns were identified: (1) crashes on low-speed stretches, involving left turn and intersections; (2) crashes involving very old drivers and older vehicles, (3) rear-end collisions on high-speed stretches; and (4) head-on and single-vehicle crashes in rural areas. Older drivers dying in the crash were over-represented in classes 2 and 4. The study shows that when older drivers are involved in fatal RTCs, they are often the ones who die (60%). Typical circumstances surrounding their involvement include manoeuvring difficulties, fast-moving traffic, and colliding in an old vehicle. Preventing fatal RTCs involving older drivers requires not only age-specific but also general measures.     

Evaluation of left-turn lane offset using the naturalistic driving study data

IntroductionThe Strategic Highway Research Program 2 (SHRP 2) Naturalistic Driving Study (NDS) data were used to evaluate gap acceptance behavior of drivers at left-turn lanes with negative, zero, or positive offsets ranging from − 29 ft to + 6 ft. The objectives of the study were to develop guidance for the design of offset left-turn lanes used as a safety countermeasure, and to provide insight regarding the use of the NDS data to future users.MethodThe study included 3350 gaps in opposing traffic evaluated by 145 NDS volunteer drivers and 275 non-NDS drivers at 14 two-way stop-controlled intersections and 44 signalized opposing left-turn pairs. Logistic regression was used to model the critical gap length for drivers as a function of offset, under conditions when their view was either blocked or not by an opposing left-turning driver.ResultsThe analysis found that the critical gap was longer at left-turn lanes with negative offsets than at those with zero or positive offsets, and was also longer when sight distance was blocked by an opposing left-turning vehicle. Sight distance was much more likely to be restricted by an opposing left-turning vehicle at negative-offset and drivers at those intersections were less likely to accept a gap when an opposing left-turn driver was present.ConclusionsLonger gap lengths could potentially result in decreased operational efficiency of an intersection. In addition, drivers making left-turns at negative-offset left-turn lanes are, on average, more likely to leave the shortest amount of time between their turn and the arrival of the next opposing through-vehicle, which may present a potential safety concern.Practical applicationsThe findings provide guidance for highway designers considering using offset left-turn lanes as a crash countermeasure. This research also highlights the benefits and limitations of using the SHRP 2 NDS data to answer similar research questions.     

The role of risk perception and other risk-related judgements in transportation mode use

AimsThe core aim of the present study was to examine the role of risk perception in use of private and public modes of transportation. An additional aim was to examine the relative importance of perception of transport risks with risk perception of non-transport factors and also to investigate differences in worry, perceived control of transportation modes, as well as trust in authorities’ risk handling, safety motivation, and attitudes towards transport safety.SampleThe results are based on a mailed self-completion questionnaire survey carried out among a representative sample of the Norwegian public aged from 18 to 65 years (n = 1864). Data collection was carried out during October–December 2008.ResultsPerceived control related to private modes of transportation, knowledge about safety and trust in authorities were found to be significantly different among respondents who often used private modes of transportation compared to those who most often used public modes. It was no significant difference in severity of consequences due to which transport modes that the respondents used most frequently.ConclusionIt may be that conclusions of previous research about the role of consequence judgement for precautionary action and demand for risk reduction are misleading when generalised to decisions about transport mode use.     

Investigate moped-car conflicts in China using a naturalistic driving study approach

ProblemMopeds are a popular transportation mode in Europe and Asia. Moped-related traffic accidents account for a large proportion of crash fatalities. To develop moped-related crash countermeasures, it is important to understand the characteristics of moped-related conflicts.MethodNaturalistic driving study data were collected in Shanghai, China from 36 car drivers. The data included 2,878 h and 78,296 km driven from 13,149 trips. Moped-car conflicts were identified and examined from the passenger car driver's perspective using kinematic trigger algorithms and manual video reduction.ResultsA total of 119 moped-car conflicts were identified, including 74 high g-force conflicts and 45 low g-force events. These conflicts were classified into 22 on-road configurations where both similarities and differences were found as compared to Western Countries. The majority of the conflicts occurred on secondary main roads and branch roads. Hard braking was the primary response that the car drivers made to these conflicts rather than hard steering.DiscussionsThe identified on-road vehicle-moped conflict configurations in Shanghai, China may be attributed to the complicated traffic environment and risky behavior of moped riders. The lower prevalence of hard steering in Shanghai as compared to the United States may be due to the lower speeds at event onsets or less available steering space, e.g., less available shoulder area on Chinese urban roads.ConclusionsThe characteristics of moped-car conflicts may impact the design of active safety countermeasures on passenger cars. The pilot data from Shanghai urban areas suggest that countermeasures developed for China may require some modifications to those developed for the United States and European countries, although this recommendation may not be conclusive given the small sample size of the study. Future studies with large samples may help better understand the characteristics of moped-car conflicts.     

Participation in driver education/training courses during graduated driver licensing,and the effect of a time-discount on subsequent traffic offenses: Findings from the New Zealand Drivers Study

IntroductionThe New Zealand GDL includes a time-discount at the restricted license stage, for attendance at an approved driver education course. This is despite international evidence showing that earlier licensure associated with a time-discount can increase risk for newly licensed drivers.ObjectiveTo examine participation in driver education courses and especially those that qualify for a time-discount; compare the profiles of course participants with non-participants; examine reasons for participation; and examine the association between a time-discount and traffic offenses once fully licensed.MethodThis study was based on the New Zealand Drivers Study (NZDS), a prospective cohort study of newly licensed drivers. Data on driver education courses were obtained at the full license interview (n = 1763), driver license and traffic offense data from the NZ Driver Licence Registry, and other data at the NZDS interviews.Results94% had heard of and 49% (n = 868) participated in a defensive driving course (DDC). No other course had more than 1% participation. Compared with the others, the DDC group were young, non-Māori, and from an area of relatively low deprivation. Through GDL, the DDC group were relatively more compliant with the conditions, and less likely to crash or receive a traffic offense notice. The groups did not differ on personality, alcohol and drug use. The reason most (85%) attended a DDC was to get their full license sooner; 86% (n = 748) received a time-discount. The time-discount group were 40% more likely to receive a traffic offense notice on their full license; this reduced to 10% after controlling for other factors.Conclusion and practical implicationsThe results of this study, when viewed in conjunction with other NZ crash evidence, indicate that a time-discount should not be given for completing a DDC or Street Talk course.     

Risk factors associated with bus accident severity in the United States: A generalized ordered logit model

IntroductionRecent years have witnessed a growing interest in improving bus safety operations worldwide. While in the United States buses are considered relatively safe, the number of bus accidents is far from being negligible, triggering the introduction of the Motor-coach Enhanced Safety Act of 2011.MethodThe current study investigates the underlying risk factors of bus accident severity in the United States by estimating a generalized ordered logit model. Data for the analysis are retrieved from the General Estimates System (GES) database for the years 2005–2009.ResultsResults show that accident severity increases: (i) for young bus drivers under the age of 25; (ii) for drivers beyond the age of 55, and most prominently for drivers over 65 years old; (iii) for female drivers; (iv) for very high (over 65 mph) and very low (under 20 mph) speed limits; (v) at intersections; (vi) because of inattentive and risky driving.     

Protective factors associated with young passenger intervening in risky driving situations

IntroductionWhile the negative influence of passengers on driving is usually studied, young passengers may protect against young drivers' crash involvement by speaking out and trying to stop unsafe driving behavior. This study sought to examine psychosocial constructs of young passengers who are likely to intervene in their friends' risky driving.MethodUniversity students aged 17 to 25 years who were single (n = 123) or in a romantic relationship (n = 130) completed an online survey measuring protective factors.ResultsThe combination of individual, friend and (for participants in a relationship) romantic partner protective factors predicted self-reported passenger intervening intentions.Impact on IndustrySince peer passengers often increase young drivers' crash risk, research on passenger intervening has significant implications for road safety strategies. The findings provide support for the operationalization of protective factors in strategies that target passenger intervening behavior.     

Peer influence predicts speeding prevalence among teenage drivers

Impact on IndustryPreventing speed-related crashes could reduce costs and improve efficiency in the transportation industry.ObjectiveThis research examined the psychosocial and personality predictors of observed speeding among young drivers.MethodSurvey and driving data were collected from 42 newly-licensed teenage drivers during the first 18 months of licensure. Speeding (i.e., driving 10 mph over the speed limit; about 16 km/h) was assessed by comparing speed data collected with recording systems installed in participants' vehicles with posted speed limits.ResultsSpeeding was correlated with elevated g-force event rates (r = 0.335, pb0.05), increased over time, and predicted by day vs. night trips, higher sensation seeking, substance use, tolerance of deviance, susceptibility to peer pressure, and number of risky friends. Perceived risk was a significant mediator of the association between speeding and risky friends.ConclusionThe findings support the contention that social norms may influence teenage speeding behavior and this relationship may operate through perceived risk.     

Does a tow-bar increase the risk of neck injury in rear-end collisions?

IntroductionDoes a tow-bar increase the risk of neck injury in the struck car in a rear-end collision? The rear part of a modern car has collision zones that are rendered nonoperational when the car is equipped with a tow-bar. Past crash tests have shown that a car's acceleration was higher in a car equipped with a tow-bar and also that a dummy placed in a car with a tow-bar had higher peak acceleration in the lower neck area.MethodThis study aimed to investigate the association between the risk of neck injury in drivers and passengers, and the presence of a registered tow-bar on the struck car in a rear-end collision. We performed a merger of police reports, the National Hospital Discharge Registry, and the National Registry of Motor Vehicles in Denmark. We identified 9,370 drivers and passengers of whom 1,519 were diagnosed with neck injury within the first year after the collision. We found a statistically insignificant 5% decrease in the risk of neck injury in the occupants of the struck car when a tow-bar was fitted compared to when it was not fitted (hazard ratio = 0.95; 95% confidence level = 0.85–1.05; p = 0.32). The result was controlled for gender, age, and the seat of the occupant. Several other collision and car characteristics and demographic information on the drivers and passengers were evaluated as confounders but were not statistically significant.ConclusionsThe present study may serve as valuable input for a meta-analysis on the effect of a tow-bar because negative results are necessary in order to avoid publication bias.     

Evaluation of an in-vehicle monitoring system (IVMS) to reduce risky driving behaviors in commercial drivers: Comparison of in-cab warning lights and supervisory coaching with videos of driving behavior

ProblemRoadway incidents are the leading cause of work-related death in the United States.MethodsThe objective of this research was to evaluate whether two types of feedback from a commercially available in-vehicle monitoring system (IVMS) would reduce the incidence of risky driving behaviors in drivers from two companies. IVMS were installed in 315 vehicles representing the industries of local truck transportation and oil and gas support operations, and data were collected over an approximate two-year period in intervention and control groups. In one period, intervention group drivers were given feedback from in-cab warning lights from an IVMS that indicated occurrence of harsh vehicle maneuvers. In another period, intervention group drivers viewed video recordings of their risky driving behaviors with supervisors, and were coached by supervisors on safe driving practices.ResultsRisky driving behaviors declined significantly more during the period with coaching plus instant feedback with lights in comparison to the period with lights-only feedback (ORadj = 0.61 95% CI 0.43–0.86; Holm-adjusted p = 0.035) and the control group (ORadj = 0.52 95% CI 0.33–0.82; Holm-adjusted p = 0.032). Lights-only feedback was not found to be significantly different than the control group's decline from baseline (ORadj = 0.86 95% CI 0.51–1.43; Holm-adjusted p > 0.05).ConclusionsThe largest decline in the rate of risky driving behaviors occurred when feedback included both supervisory coaching and lights.Practical applicationsSupervisory coaching is an effective form of feedback to improve driving habits in the workplace. The potential advantages and limitations of this IVMS-based intervention program are discussed.