Analysis of factors associated with injury severity in crashes involving young New Zealand drivers

Young people are a risk to themselves and other road users, as motor vehicle crashes are the leading cause of their death. A thorough understanding of the most important factors associated with injury severity in crashes involving young drivers is important for designing well-targeted restrictive measures within youth-oriented road safety programs. The current study estimates discrete choice models of injury severity of crashes involving young drivers conditional on these crashes having occurred. The analysis examined a comprehensive set of single-vehicle and two-vehicle crashes involving at least one 15–24 year-old driver in New Zealand between 2002 and 2011 that resulted in minor, serious or fatal injuries. A mixed logit model accounting for heterogeneity and heteroscedasticity in the propensity to injury severity outcomes and for correlation between serious and fatal injuries proved a better fit than a binary and a generalized ordered logit. Results show that the young drivers’ behavior, the presence of passengers and the involvement of vulnerable road users were the most relevant factors associated with higher injury severity in both single-vehicle and two-vehicle crashes. Seatbelt non-use, inexperience and alcohol use were the deadliest behavioral factors in single-vehicle crashes, while fatigue, reckless driving and seatbelt non-use were the deadliest factors in two-vehicle crashes. The presence of passengers in the young drivers’ vehicle, and in particular a combination of males and females, dramatically increased the probability of serious and fatal injuries. The involvement of vulnerable road users, in particular on rural highways and open roads, considerably amplified the probability of higher crash injury severity.     

Deaths of teenagers as passengers in motor vehicles

Teenagers far exceed all other ages in fatalities per capita both as drivers and as passengers in motor vehicles. Most studies of vehicle crashes involving teenagers focus on teenage drivers, despite the fact that the numbers of teenage deaths as passengers and as drivers are about equal. In 1978, 63% of all fatally injured teenage passengers sustained their injuries in vehicles driven by teenage drivers: 72% of the passengers fatally injured in vehicles driven by teenage drivers were teenagers. Half of the teenage passenger deaths occurred in nighttime crashes. Possible ways to reduce the crash deaths of teenagers are discussed. These include restricting the driving of teenagers; prohibiting teenage drivers from transporting teenage passengers; greater implementation of crash packaging technologies; cleaning up highway and roadside hazards, and laws requiring seat belt use by teenagers.     

Increased risk of driver fatality due to unrestrained rear-seat passengers in severe frontal crashes

While belt usage among rear-seat passengers is disproportionately lower than their front-seat counterpart, this may have serious consequences in the event of a crash not only for the unbelted rear-seat passenger but also for the front-seat passengers as well. To quantify that effect, the objective of the study is to evaluate the increased likelihood of driver fatality in the presence of unrestrained rear-seat passengers in a severe frontal collision. U.S.-based census data from 2001 to 2009 fatal motor vehicle crashes was used to enroll frontal crashes which involved 1998 or later year vehicle models with belted drivers and at least one adult passenger in the rear left seat behind the driver. Results using multivariate logistic regression analysis indicated that the odds of a belt restrained driver sustaining a fatal injury was 137% (95% CI = 95%, 189%) higher when the passenger behind the driver was unbelted in comparison to a belted case while the effects of driver age, sex, speed limit, vehicle body type, airbag deployment and driver ejection were controlled in the model. The likelihood of driver fatality due to an unrestrained rear left passenger increased further (119–197%) in the presence of additional unrestrained rear seat passengers in the rear middle or right seats. The results from the study highlight the fact that future advances to front row passive safety systems (e.g. multi-stage airbag deployment) must be adapted to take into account the effect of unrestrained rear-seat passengers.     

Effect of bus size and operation to crash occurrences

This paper evaluates roadway and operational factors considered to influence crashes involving buses. Factors evaluated included those related to bus sizes and operation services. Negative binomial (NB) and multinomial logit (MNL) models were used in linearizing and quantifying these factors with respect to crash frequency and injury severities, respectively. The results showed that position of the bus travel lane, presence or absence of on-street shoulder parking, posted speed limit, lane width, median width, number of lanes per direction and number of vehicles per lane has a higher influence on bus crashes compared to other roadway and traffic factors. Wider lanes and medians were found to reduce probability of bus crashes while more lanes and higher volume per lane were found to increase the likelihood of occurrences of bus-related crashes. Roadways with higher posted speed limits excluding freeways were found to have high probability of crashes compared to low speed limit roadways. Buses traveling on the inner lanes and making left turns were found to have higher probability of crashes compared to those traveling on the right most lanes. The same factors were found to influence injury severity though with varying magnitudes compared to crash frequency.     

What can we learn about North Dakota's youngest drivers from their crashes?

For North Dakota teens, three of every four deaths are from motor vehicle crashes. Injury crash records for teen drivers were studied to gain insight regarding driver, vehicle, and road factors for public safety policy and program discussions. Results show 14-year-old drivers are three times more likely to die or be disabled in an injury crash than 17-year-old drivers, and that male drivers are 30% less likely to incur severe injury. As expected, seat belt use is a critical factor in severe injury avoidance. The likelihood for death or disablement is 165% greater for unbelted teen drivers than for those who are properly belted. In addition, rural and gravel roads pose a risk. Teens are six times more likely to be severely injured in crashes on rural roads than on urban roads. Findings suggest that an increased licensing age and seat belt emphasis may reduce teen traffic injuries in the state. In addition, more information on exposure should be attained to better understand rural and gravel road as risks.     

Examining the influence of aggressive driving behavior on driver injury severity in traffic crashes

In this paper, we capture the moderating effect of aggressive driving behavior while assessing the influence of a comprehensive set of variables on injury severity. In doing so, we are able to account for the indirect effects of variables on injury severity through their influence on aggressive driving behavior, as well as the direct effect of variables on injury severity. The methodology used in the paper to accommodate the moderating effect of aggressive driving behavior takes the form of two models – one for aggressive driving and another for injury severity. These are appropriately linked to obtain the indirect and direct effects of variables. The data for estimation is obtained from the National Motor Vehicle Crash Causation Study (NMVCCS). From an empirical standpoint, we consider a fine age categorization until 20 years of age when examining age effects on aggressive driving behavior and injury severity.There are several important results from the empirical analysis undertaken in the current paper based on post-crash data collection on aggressive behavior participation just prior to the crash and injury severity sustained in a crash. Young drivers (especially novice drivers between 16 and 17 years of age), drivers who are not wearing seat belt, under the influence of alcohol, not having a valid license, and driving a pick-up are found to be most likely to behave aggressively. Situational, vehicle, and roadway factors such as young drivers traveling with young passengers, young drivers driving an SUV or a pick-up truck, driving during the morning rush hour, and driving on roads with high speed limits are also found to trigger aggressive driving behavior. In terms of vehicle occupants, the safest situation from a driver injury standpoint is when there are two or more passengers in the vehicle, at least one of whom is above the age of 20 years. These and many other results are discussed, along with implications of the result for graduated driving licensing (GDL) programs.     

Improving seat belt use among teen drivers: Findings from a service-learning approach

Background

Low seat belt use and higher crash rates contribute to persistence of motor vehicle crashes as the leading cause of teenage death. Service-learning has been identified as an important component of public health interventions to improve health behavior.

Methodology

A service-learning intervention was conducted in eleven selected high schools across the United States in the 2011–2012 school year. Direct morning and afternoon observations of seat belt use were used to obtain baseline observations during the fall semester and post-intervention observations in the spring. The Mann–Whitney U test for 2 independent samples was used to evaluate if the intervention was associated with a statistically significant change in seat belt use. We identified factors associated with seat belt use post-intervention using multivariable logistic regression.

Results

Overall seat belt use rate increased by 12.8%, from 70.4% at baseline to 83.2% post-intervention (p < 0.0001). A statistically significant increase in seat belt use was noted among white, black, and Hispanic teen drivers. However, black and Hispanic drivers were still less likely to use seat belts while driving compared to white drivers. Female drivers and drivers who had passengers in their vehicle had increased odds of seat belt use.

Conclusion

A high school service-learning intervention was associated with improved seat belt use regardless of race, ethnicity, or gender, but did not eliminate disparities adversely affecting minority youth. Continuous incorporation of service-learning in high school curricula could benefit quality improvement evaluations aimed at disparities elimination and might improve the safety behavior of emerging youth cohorts.     

Passenger seating position and the risk of passenger death or injury in traffic crashes

OBJECTIVE: To estimate the association of passenger seat position with the risk of death and serious injury for passengers in traffic crashes. METHODS: Using 1993-2000 data from the National Highway Traffic Safety Administration's Crashworthiness Data System (CDS), the risk ratio for death and serious injury was estimated for rear seat passengers compared with front seat passengers in motor vehicle crashes. RESULTS: The adjusted risk ratio for death of passengers in the rear seat in a crash was 0.61 (95% confidence interval (CI) 0.46-0.81). Rear seat passenger position was also associated with a decrease in the risk of death and serious injury compared with the front seat passenger position: risk ratio=0.67 (95% CI 0.57-0.78). CONCLUSION: We estimated that the rear seat passenger position may reduce the risk of death in a motor vehicle crash by about 39% and reduce the risk of death or serious injury in a crash by 33%, compared with the front seat passenger position. If the associations that we report are causal, sitting in the rear seat, compared with the front seat, may prevent about 4 in 10 passenger deaths, or 3 in 10 passenger deaths and injuries, that might otherwise occur.     

Exploring factors contributing to injury severity at freeway merging and diverging locations in Ohio

Identifying factors that affect crash injury severity and understanding how these factors affect injury severity is critical in planning and implementing highway safety improvement programs. Factors such as driver-related, traffic-related, environment-related and geometric design-related were considered when developing statistical models to predict the effects of these factors on the severity of injuries sustained from motor vehicle crashes at merging and diverging locations. Police-reported crash data at selected freeway merging and diverging areas in the state of Ohio were used for the development of the models. A generalized ordinal logit model also known as partial proportional odds model was applied to identify significant factors increasing the likelihood of one of the five KABCO scale of injury severity: no injuries, possible/invisible injuries, non-incapacitating injuries, incapacitating injuries, or fatal injuries. The results of this study show that semi-truck related crashes, higher number of lanes on freeways, higher number of lanes on ramps, speeding related crashes, and alcohol related crashes tend to increase the likelihood of sustaining severe injuries at freeway merging locations. In addition, females and older persons are more likely to sustain severe injuries especially at freeway merge locations. Alcohol related crashes, speeding related crashes, angle-type collisions, and lane-ramp configuration type D significantly increase the likelihood of severe injury crashes at diverging areas. Poor lighting condition tends to increase non-incapacitating injuries at diverging areas only. Moreover, adverse weather condition increases the likelihood of no-injury and fatal injuries at merging areas only and adverse road conditions tend to increase a range of injury severity levels from possible/invisible injuries to incapacitating injuries at merging areas only.     

The influence of driver distraction on the severity of injuries sustained by teenage drivers and their passengers

Studies show that teenage drivers are at a higher risk for crashes. Opportunities to engage in technology and non-technology based distractions appear to be a particular concern among this age group. An ordered logit model was developed to predict the likelihood of a severe injury for these drivers and their passenger using a national crash database (the 2003, U.S. DOT-General Estimate System [GES]). As one would expect, speeding substantially increases the likelihood of severe injuries for teenage drivers and their passengers. The results of the analysis also reveal that teenage drivers have an increased likelihood of more severe injuries if distracted by a cell phone or by passengers than if the source of distraction was related to in-vehicle devices or if the driver was inattentive. Additionally, passengers of teenage drivers are more likely to sustain severe injuries when their driver is distracted by devices or passengers than with a non-distracted or inattentive driver. This supports the previous literature on teenage drivers and extends our understanding of injuries for this age group related to distraction-related crashes.     

Rollover crashes: predicting serious injury based on occupant, vehicle, and crash characteristics

The purpose of this research was to determine occupant, vehicle, and crash characteristics predicting serious injury during rollover crashes. We compared 27 case occupants with serious or greater severity injuries with 606 control occupants without injury or with only minor or moderate injury. Odds ratios (OR) for individual variables and logistic regression were used to identify predictive variables for serious injury associated with rollovers. Cases more often had thorax, spine, or head injury compared to controls that more often had extremity injuries. Intrusion (especially roof rail or B-pillar intrusion) at the occupant's position, the vehicle interior side and roof as sources of injury, and improper safety belt use were significantly associated with serious injury. Even when safety belt use or proper use was controlled for, occupants with greater magnitude of intrusion at their seat position were about 10 times more likely to receive serious injury. Although prevention of rollover crashes is the ultimate goal, it is important to develop safer vehicles and safety systems to better protect occupants who are involved in rollover crashes. This also requires improvement in data collection systems documenting these types of crashes.     

The effect of seat belts on minor and severe injuries measured on the abbreviated injury scale

Following the implementation of seat belt wearing legislation in Victoria in December 1970, the Royal Australasian College of Surgeons established a survey to collect detailed injury and crash data from car accidents in that State. An analysis of the effect of seat belt wearing on severe injuries sustained by car occupants during the first two years of the survey was reported by Cameron and Nelson[1977]. Minor injuries were ignored in that analysis. Further work extended the file to cover 8537 occupants injured during the first three years of the survey and the injuries (including minor injuries) were coded on the Abbreviated Injury Scale. This paper examines the effect of seat belt wearing on both minor and severe injuries. Some comparisons of injury severity distributions in the Victorian data and in data collected by North American MDAI teams are also made. The paper concludes that the wearing of static three-point lap/sash belts by front outboard seat occupants of cars and car derivatives is associated with: (a) Reduced likelihood of severe-to-fatal injury to the head-face, thorax, lower torso and lower extremities when injured and not ejected in crashes in built-up areas and, for some body regions, in open road crashes, (b) Increased likelihood of minor injury to the thorax and lower torso when injured and not ejected in crashes in all locations and of minor injury to the neck (i.e. whiplash) when injured and not ejected in crashes in built-up areas. There are suggestions that the increased likelihoods of the minor injuries are not artefacts of the injury criterion for inclusion, nor of the reduced likelihood of severe injury to the trunk when seat belts are worn, but are due to the wearing of the seat belt.     

Injury trends of passenger car drivers in frontal crashes in the USA

Injuries trends of passenger car drivers in head-on collisions are identified based on crash data extracted from the National Automotive Sampling System. Annual injury incidence levels are estimated for years 1990-2007. Over that period, the number of crashes is predicted to rise by 71%. However, the number of serious injuries to drivers is expected to rise by only 41% and driver fatalities are anticipated to decrease by 9%. Meantime, the types of injuries suffered by drivers are changing. Year-to-year shifts in injury patterns result from changes in vehicle size classes within the US vehicle fleet population and increases in seat belt use and air bag availability. The effectiveness of air bags in saving lives is estimated to be 30%, and with more air bag-equipped cars on the road, the probability of sustaining a life-threatening head or a torso injury is reduced. Air bags, however, are not as effective in preventing upper and lower extremity injuries, and thus arm and leg injuries will become more prevalent in years to come.     

Pregnant women in vehicles: Driving habits,position and risk of injury

This study proposed to broadly examine vehicle use by pregnant women in order to improve realism of accident simulations involving these particular occupants. Three research pathways were developed: the first consisted in a questionnaire survey examining the driving habits of 135 pregnant women, the second obtained measurements of 15 pregnant women driving position in their own vehicle from the 6th to the 9th month of pregnancy by measuring distances between body parts and vehicle parts, and the third examined car accidents involving pregnant occupants. Results obtained indicate that between 90% and 100% of pregnant women wore their seat belts whatever their stage of pregnancy, although nearly one third of subjects considered the seat belt was dangerous for their unborn child. The measurements obtained also showed that the position of the pregnant woman in her vehicle, in relation to the various elements of the passenger compartment, changed significantly during pregnancy. In the studied accidents, no correlation was found between the conditions of the accident and the resulting fetal injury. Results reveal that pregnant women do not modify significantly the seat setting as a function of pregnancy stage. Only the distance between maternal abdomen and steering wheel change significantly, from 16 cm to 12 cm at 6 and 9 month respectively. Pregnant women are mainly drivers before 8 months of pregnancy, passengers after that. Car use frequency falls down rapidly from 6 to 9 months of pregnancy. Real crashes investigations indicate a low rate of casualties, i.e. 342 car accidents involving pregnant women for a period of 9 years in an approximately 1.7 million inhabitants area. No specific injury was found as a function of stage of pregnancy.     

An examination of the environmental,driver and vehicle factors associated with the serious and fatal crashes of older rural drivers

Motor vehicle crashes involving rural drivers aged 75 years and over are more than twice as likely to result in a serious or fatal injury as those involving their urban counterparts. The current study examined some of the reasons for this using a database of police-reported crashes (2004–2008) to identify the environmental (lighting, road and weather conditions, road layout, road surface, speed limit), driver (driver error, crash type), and vehicle (vehicle age) factors that are associated with the crashes of older rural drivers. It also determined whether these same factors are associated with an increased likelihood of serious or fatal injury in younger drivers for whom frailty does not contribute to the resulting injury severity. A number of environmental (i.e., undivided, unsealed, curved and inclined roads, and areas with a speed limit of 100 km/h or greater) and driver (i.e., collision with a fixed object and rolling over) factors were more frequent in the crashes of older rural drivers and additionally associated with increased injury severity in younger drivers. Moreover, when these environmental factors were entered into a logistic regression model to predict whether older drivers who were involved in crashes did or did not sustain a serious or fatal injury, it was found that each factor independently increased the likelihood of a serious or fatal injury. Changes, such as the provision of divided and sealed roads, greater protection from fixed roadside objects, and reduced speed limits, appear to be indicated in order to improve the safety of the rural driving environment for drivers of all ages. Additionally, older rural drivers should be encouraged to reduce their exposure to these risky circumstances.     

Why Turks do not use seat belts? An interview study

Despite the effectiveness of seat belt use and legislation, seat belt use rate is low in Turkey. The aim of this study was to investigate the motives to use and not to use a seat belt in different traveling conditions in a sample of car drivers and passengers. Interviews were made face to face with 221 interviewees from different age and occupation groups. Frequently reported reasons for using a seat belt were traveling conditions, safety, situational conditions, habit of using a seat belt, and avoiding punishment. Frequently reported reasons for not using a seat belt were situational conditions, not believing in the effectiveness, discomfort and having no habit. Safety was the strongest predictor of reported seat belt use in both low and high risk traveling conditions. Findings suggest that seat belt campaigns should mainly emphasize seat belt's safety impact and aim at habit formation.     

A joint econometric analysis of seat belt use and crash-related injury severity

This paper formulates a comprehensive econometric structure that recognizes two important issues in crash-related injury severity analysis. First, the impact of a factor on injury severity may be moderated by various observed and unobserved variables specific to an individual or to a crash. Second, seat belt use is likely to be endogenous to injury severity. That is, it is possible that intrinsically unsafe drivers do not wear seat belts and are the ones likely to be involved in high injury severity crashes because of their unsafe driving habits. The preceding issues are considered in the current research effort through the development of a comprehensive model of seat belt use and injury severity that takes the form of a joint correlated random coefficients binary-ordered response system. To our knowledge, this is the first instance of such a model formulation and application not only in the safety analysis literature, but in the econometrics literature in general. The empirical analysis is based on the 2003 General Estimates System (GES) data base. Several types of variables are considered to explain seat belt use and injury severity levels, including driver characteristics, vehicle characteristics, roadway design attributes, environmental factors, and crash characteristics. The results, in addition to confirming the effects of various explanatory variables, also highlight the importance of (a) considering the moderating effects of unobserved individual/crash-related factors on the determinants of injury severity and (b) seat belt use endogeneity. From a policy standpoint, the results suggest that seat belt non-users, when apprehended in the act, should perhaps be subjected to both a fine (to increase the chances that they wear seat belts) as well as mandatory enrollment in a defensive driving course (to attempt to change their aggressive driving behaviors).     

Risky driving related to driver and vehicle characteristics

This investigation was performed to determine relationships between driver and vehicle characteristics and risk taking in everyday driving, as measured by close following in freeway traffic. A total of 12,000 observations were made of headways (time intervals between successive vehicles) in high flow freely moving freeway traffic at two sites, one in Michigan, the other in Toronto, Canada. The headways were measured using a photographic technique which allowed vehicle and occupant characteristics to be recorded, including type of vehicle and sex and seat belt use. For the Michigan observations, the vehicle license number was recorded, from which additional information on the vehicle and owner (usually the driver) was obtained from state files, including the vehicle mass and model year and the owner's age. sex and history of recorded accidents and traffic violations. Shorter headways, corresponding to higher risk, were found for drivers with prior accidents or violations, young drivers, male drivers, drivers with no passengers. and drivers who did not wear a seat belt. Vehicles associated with shorter headways included newer cars and cars of intermediate mass (1600–1900 kg).     

Belt use by high-risk drivers before and after New York's seat belt use law

Belt use among drivers traveling on limited access highways was observed before and after New York's mandatory seat belt use law. The results showed that high-speed drivers had lower belt use rates before the law and increased their belt use less in response to the law. Belt use rates before the law were 25%, 29%, and 28% for the high-, medium-, and low-speed groups as compared with 51%, 64%, and 57%, respectively, after the law. High-speed drivers also had inferior previous driving records, confirming their higher risk of motor vehicle crash involvement.     

Attitudes of commercial motor vehicle drivers towards safety belts

Despite the fact that Hawaii has one of the highest seat belt use rates for passenger vehicles in the United States, and has had a mandatory seat belt use law since the 1980s, studies have shown that commercial motor vehicles (CMV) seat belt use rates are low. To better understand this phenomenon, a comprehensive survey of commercial vehicle drivers was conducted in Hawaii to ascertain attitudes and self-reported behaviors regarding seat belt use. A total of 791 drivers responded to a written questionnaire implemented at weigh stations and distributed to various trucking firms and transport centers. Approximately 67% reported that they use seat belts “always” when driving a CMV (commercial motor vehicle), yet when asked how often do other CMV drivers use seat belts, only 31% responded “always.” Interestingly, 86% of these same drivers reported that they use seat belts “always” when driving a personal vehicle. The major reason cited for non-use of belts was “frequent stops/inconvenience” (29%), and “not safety conscious” (23%). Notably, the self-reported use of safety belts is highest among operators of vans (88% said “always”), followed by buses (87% said “always”) and lowest among truck drivers (only 60% said “always”). In this paper, some of the differences between self-reported users and non-users are explored and a multivariate logit model was developed to predict the odds of belt use as a function of various factors.