Brian C Tefft

Graduated driver licensing research, 2010-present

This is the latest in a series of reviews of research on graduated driver licensing (GDL) published in the Journal of Safety Research, covering the period January 1, 2010-June 1, 2012 and works in progress. The intent is to keep researchers and policy makers current regarding the existing state of knowledge about GDL, and to identify information gaps and areas where clarification of research findings are needed. The recent research indicates that we continue to learn about ways to extend GDL benefits, but there remain important questions in need of further inquiry. In terms of impact on industry, the review provides guidance for the future GDL research agenda.

Impact speed and a pedestrian's risk of severe injury or death

This study estimates the risk of severe injury or death for pedestrians struck by vehicles using data from a study of crashes that occurred in the United States in years 1994-1998 and involved a pedestrian struck by a forward-moving car, light truck, van, or sport utility vehicle. The data were weighted to correct for oversampling of pedestrians who were severely injured or killed. Logistic regression was used to adjust for potential confounding related to pedestrian and vehicle characteristics. Risks were standardized to represent the average risk for a pedestrian struck by a car or light truck in the United States in years 2007-2009. Results show that the average risk of a struck pedestrian sustaining an injury of Abbreviated Injury Scale 4 or greater severity reaches 10% at an impact speed of 17.1miles per hour (mph), 25% at 24.9mph, 50% at 33.0mph, 75% at 40.8mph, and 90% at 48.1mph. The average risk of death reaches 10% at an impact speed of 24.1mph, 25% at 32.5mph, 50% at 40.6mph, 75% at 48.0mph, and 90% at 54.6mph. Risks varied by age. For example, the average risk of death for a 70-year-old pedestrian struck at any given speed was similar to the average risk of death for a 30-year-old pedestrian struck at a speed 11.8mph faster.

Prevalence of motor vehicle crashes involving drowsy drivers, United States, 1999-2008

The proportion of motor vehicle crashes that involve a drowsy driver likely is greater than existing crash databases reflect, due to the possibility that some drivers whose pre-crash state of attention was unknown may have been drowsy. This study estimated the proportion of crashes that involved a drowsy driver in a representative sample of 47,597 crashes in the United States from 1999 through 2008 that involved a passenger vehicle that was towed from the scene. Multiple imputation was used to address missing data on driver drowsiness. In the original (non-imputed) data, 3.9% of all crashes, 7.7% of non-fatal crashes that resulted in hospital admission, and 3.6% of fatal crashes involved a driver coded as drowsy; however, the drowsiness status of 45% of drivers was unknown. In the imputed data, an estimated 7.0% of all crashes (95% confidence interval: 4.6%, 9.3%), 13.1% of non-fatal crashes that resulted in hospital admission (95% confidence interval: 8.8%, 17.3%), and 16.5% of fatal crashes (95% confidence interval: 12.5%, 20.6%) involved a drowsy driver. Results suggest that the prevalence of fatal crashes that involve a drowsy driver is over 350% greater than has been reported previously.

Teen Driver Risk in Relation to Age and Number of Passengers, United States, 2007–2010

Objective: To provide updated estimates of the relationship between the number and ages of passengers present in a vehicle and the crash risk per mile driven of 16- and 17-year-old drivers. Methods: Data on crashes that occurred in years 2007–2010 and data on the number of miles driven in years 2008–2009 were examined. Rates of crash involvement and driver death per mile driven were estimated for 16- and 17-year-old drivers with no passengers; with 1, 2, and 3 or more passengers younger than age 21 (and no older passengers); and with at least 1 passenger aged 35 or older. Results: For 16- and 17-year-old drivers, having 1 passenger younger than age 21 (and no older passengers) was associated with 44 percent greater risk per mile driven of being killed in a crash, compared to having no passengers (relative risk [RR]: 1.44, 95% confidence interval [CI]: 1.01–2.04). Having 2 passengers younger than age 21 was associated with double the risk of being killed in a crash, compared to having no passengers (RR: 2.02, 95% CI: 1.36–2.99). Having 3 or more passengers younger than age 21 was associated with roughly quadruple the risk of being killed in a crash, compared to having no passengers (RR: 4.39, 95% CI: 1.45–13.31). The relative risk of being involved in any police-reported crash in the presence of young passengers followed a similar pattern; however, the differences in risks of being involved in any police-reported crash were smaller and were not statistically significant. Having at least 1 passenger aged 35 or older in the vehicle was associated with a 62 percent lower risk per mile driven of being killed in a crash (RR: 0.38, 95% CI: 0.24–0.60) and a 46 percent lower risk of being involved in any police-reported crash (RR: 0.54, 95% CI: 0.31–0.93) for 16- and 17-year-old drivers, compared to having no passengers. Conclusions: These results show that although the overall number of teen driver fatalities has decreased substantially over the past several years, carrying young passengers is still a significant risk factor for young drivers. In contrast, carrying adult passengers is associated with significantly lower risk of crash involvement.

Characteristics of teens-with-teens fatal crashes in the United States, 2005–2010

BACKGROUND More than 40% of fatal crashes of 16- and 17-year-old drivers occur when transporting teenagers. Characteristics of this predominant crash type and prevention possibilities are described, based on data from fatal crashes in the United States during 2005-2010. RESULTS Fifty-seven percent of 16- and 17-year old drivers in fatal crashes had at least one passenger. Most commonly, all passengers were ages 13-19 (42% of all drivers and 73% of those with passengers). Of fatal crashinvolved drivers with teenage passengers and no passengers of other ages, 56% had one passenger, 24% had two, and 20% had three or more. Most frequently, passengers were the same sex and within one year of the driver. Risk factors involving speeding, alcohol use, late-night driving, lack of a valid license, seat belt non-use, and crash responsibility were more prevalent with teenage passengers than when driving alone, and the prevalence of these factors increased with the number of teenage passengers. Many risk factors were most prevalent with passengers ages 20-29, although few crashes had this occupant configuration. Risk factors were least prevalent with a passenger 30 or older. DISCUSSION Fatal crashes of 16- and 17-year-old drivers with teen passengers are a common crash scenario, despite passenger restrictions in 42 states and the District of Columbia during some or all of the study period. The proportion of these fatal crashes decreased slightly from 46% in 1995 (pre-GDL) to 43% in 2010 and showed no signs of decreasing during the six-year study period (range 41% to 43%). PRACTICAL APPLICATIONS Existing passenger restrictions are relatively weak and could be strengthened. Fatal crashes involving teen passengers, especially multiple passengers, are more likely to involve alcohol, late-night driving, driver error, and invalid licensure, so stepped-up enforcement of existing laws involving these behaviors might reduce the prevalence of such crashes.

Comparison of older and younger novice driver crash rates: Informing the need for extended Graduated Driver Licensing restrictions

BACKGROUND Few previous studies have directly compared crash rates of older and younger novice drivers. To inform discussion about whether Graduated Driver Licensing (GDL) policies that are applied in the US for younger novice drivers should be applied to older novice drivers, we conducted a longitudinal study to examine overall, nighttime, and multiple passenger crash rates over the initial four years of licensure differ for novice drivers licensed at different ages. METHODS Using data from the New Jersey Traffic Safety Outcomes (NJ-TSO) data warehouse, we selected all NJ drivers who obtained their initial intermediate drivers license from 2006 through 2014 and had at least one month of follow-up from the date of licensure to study end or death (n=1,034,835). Novice drivers were grouped based on age at licensure: age 17; 18-20; 21-24; and 25 or older. We estimated monthly rates for overall crashes (per 10,000 licensed drivers) as well as: late night crashes (11:01 p.m.-4:59 a.m.); early night crashes (9:00 p.m.-11:00 p.m.); and multiple passenger crashes (two or more passengers). Average monthly rates were calculated for specific relevant time periods and Poisson regression models were used to compare rates: (1) between novice driver groups with the same time since licensure; (2) over the first 48 months of licensure within each novice driver group; and (3) between same-aged 21-year-old drivers with varying lengths of licensure. RESULTS Although initial (three months post-licensure) overall crash rates of novice NJ drivers age 21 and older were higher than rates of same-aged experienced drivers, they were substantially lower than initial rates for 17- to 20-year-old novice drivers, who are licensed under GDL policies. Moreover, older novice drivers experience much less steep crash reductions over the first year of licensure than younger novice drivers. Nighttime crash rates among the 21- to 24-year old and aged 25 and older novice driver groups were stable over the first year of licensure. For novice drivers under age 21, early night crash rates declined rapidly over the course of licensure, while changes in late night crashes were much smaller. First-year multiple passenger crash rates were highest for drivers licensed at age 18-20, and novice driver groups experienced varying amounts of reduction in multiple passenger crashes over time. CONCLUSIONS Study findings support NJs current GDL policies for 17- to 20-year-old novice drivers and the potential for added benefits from beginning the nighttime restriction at 9:00 p.m. Conversely, there was a lack of compelling evidence for additional policies for drivers licensed at age 21-24 and no evidence to indicate a need for additional GDL policies for NJ novices aged 25 years and older.

Newer Model Years Are Associated with Reduced Risk of Motor Vehicle Crash Fatalities among Older Drivers

Older drivers are a growing and particularly vulnerable population. Advances in vehicle safety may reduce the risk of death in the event of a motor vehicle crash (MVC). Although previous studies have identified a relationship between increasing model years and decreased risk of death in MVC among adult drivers, this relationship has not been quantified among older drivers. The purpose of this study was to examine the relationship between vehicle model year and the risk of death among drivers aged 65 years and older who were involved in MVCs in the United States from 2010 to 2015. Data were from a census of all fatal MVCs and a representative sample of all police-reported crashes nationwide. Drivers were stratified into five age groups (65–69, 70–74, 75–79, 80–84, and 85+). Vehicles examined were cars, sport utility vehicles, pick-up trucks, and vans. Overall, older drivers driving vehicles older than model year 1990 were more than twice as likely to be killed in a crash as individuals driving vehicles of model years 2000 to 2009. Older drivers driving vehicles of model years 2010 and newer had 46% lower risk of MVC death than those driving vehicles of model year 2000 to 2009. The relationship between vehicle model year and risk of death in a crash varied by driver age and vehicle type, however, the same overall patterns were observed for all age groups and vehicle types examined. These findings suggest that older adults are responsive to improvements in vehicle safety.

Acute sleep deprivation and culpable motor vehicle crash involvement

Study Objectives To quantify the relationship between acute sleep deprivation and culpable involvement in motor vehicle crashes. Methods Participants were 6845 drivers involved in a representative sample of crashes investigated by the US Department of Transportation in years 2005-2007. A modified case-control study design was used to compare self-reported hours of sleep in the 24 hr before crashing between drivers deemed culpable versus nonculpable. Analyses controlled for fatigue-related, driver-related, and environmental factors. Specific errors that led to crashes were also examined. Results Drivers who reported having slept for 6, 5, 4, and less than 4 hr in the 24 hr before crashing had 1.3 (95% confidence interval [CI] = 1.04 to 1.7), 1.9 (1.1 to 3.2), 2.9 (1.4 to 6.2), and 15.1 (4.2 to 54.4) times the odds, respectively, of having been culpable for their crashes, compared with drivers who reported 7-9 hr of sleep. Drivers who had slept less than 4 hr had 3.4 (95% CI = 2.1 to 5.6) times the increase in odds of culpable involvement in single-vehicle crashes compared with multiple-vehicle crashes. Recent change in sleep schedule, typically feeling drowsy upon waking, and driving for 3+ hr were also associated with culpability (all p ≤ 0.013). Assuming nonculpable drivers comprised a representative sample of all drivers present where crashes occurred, these odds ratios approximate incidence rate ratios for culpable crash involvement per unit of time driving. Conclusions Driving after having slept less than 7 hr in a 24 hr period is associated with elevated risk of culpable crash involvement. Risk is greatest for drivers who have slept less than 4 hr and is manifested disproportionately in single-vehicle crashes.

Do the benefits outweigh the costs? Societal benefit-cost analysis of three large truck safety technologies

Although research has found advanced safety technologies to be effective at preventing large truck crashes, limited empirical data exists regarding their cost effectiveness to the U.S. society. Without these data, carriers are hesitant to adopt costly technologies and government agencies are hesitant to create regulation mandating their use. The objective of this study was to provide scientifically-based estimates of the societal benefits and costs of large truck automatic emergency braking (AEB), lane departure warning (LDW), and video-based onboard safety monitoring (OSM). For each technology, benefit-cost analyses were performed for installing the technology on all large trucks (including retrofitting existing trucks) and for equipping new large trucks only. Sensitivity analyses examined three cost estimates (low, average, high; values technology-specific), two estimates of system efficacy (low and high; values technology-specific), and three discount rates (0%, 3%, 7%) for each technology. Equipping trucks with LDW and video-based OSM systems were found to be cost effective for all combinations of costs, efficacy, and discount rates examined, for both new and existing trucks. Results for AEB and were mixed. Only a

PW 2529 Extending graduated driver licensing policy to older novice drivers: a critical analysis of current evidence

500 AEB system was cost effective when equipping new trucks and retrofitting existing trucks. However, all cost estimates were cost effective with a 28% efficacy rate when only equipping new large trucks. Overall, these data suggested all three technologies can be cost-effective for new large trucks provided the current costs and efficacy rates can be maintained or improved upon.