Neil Lerner

Using the U.S. National Household Travel Survey to estimate the impact of passenger characteristics on young drivers’ relative risk of fatal crash involvement

Motor vehicle crashes are the main cause of morbidity and mortality in teenagers and young adults in the United States. Driving exposure and passenger presence, which can both vary by driver and passenger characteristics, are known to influence crash risk. Some studies have accounted for driving exposure in calculating young driver fatal crash risk in the presence of passengers, but none have estimated crash risk by driver sex and passenger age and sex. One possible reason for this gap is that data collection on driving exposure often precludes appropriate analyses. The purpose of this study was to examine, per 10 million vehicle trips (VT) and vehicle-miles traveled (VMT), the relative risk of fatal crash involvement in 15-20-year-old male and female drivers as a function of their passengers age and sex, using solo driving as the referent. The Fatality Analysis Reporting System provided fatal motor vehicle crash data from 1999 to 2003 and the 2001 National Household Travel Survey (NHTS) provided VT and VMT. The NHTS collects driving exposure for both household and non-household members (e.g., friends, colleagues), but demographic characteristics only on household members. Missing age and sex of non-household passengers were imputed with hot deck using information from household passengers trips with non-household drivers, thereby enabling the calculation of crash rate and relative risk estimates based upon driver and passenger characteristics. Using this approach, the highest risk was found for young male drivers with 16-20-year-old passengers (relative risk [RR] per 10 million VT=7.99; 95% confidence interval [CI], 7.34-8.69; RR per 10 million VMT=9.94; 95% CI, 9.13-10.81). Relative risk was also high for 21-34-year-old passengers, again particularly when both drivers and passengers were male. These effects warrant further investigation and underscore the importance of considering driving exposure by passenger characteristics in understanding crash risk. Additionally, as all imputation techniques are imperfect, a more accurate estimation of U.S. fatal crash risk per distance driven would require national surveys to collect data on non-household passenger characteristics.

Detecting and Quantifying Mind Wandering during Simulated Driving

Mind wandering is a pervasive threat to transportation safety, potentially accounting for a substantial number of crashes and fatalities. In the current study, mind wandering was induced through completion of the same task for 5 days, consisting of a 20-min monotonous freeway-driving scenario, a cognitive depletion task, and a repetition of the 20-min driving scenario driven in the reverse direction. Participants were periodically probed with auditory tones to self-report whether they were mind wandering or focused on the driving task. Self-reported mind wandering frequency was high, and did not statistically change over days of participation. For measures of driving performance, participant labeled periods of mind wandering were associated with reduced speed and reduced lane variability, in comparison to periods of on task performance. For measures of electrophysiology, periods of mind wandering were associated with increased power in the alpha band of the electroencephalogram (EEG), as well as a reduction in the magnitude of the P3a component of the event related potential (ERP) in response to the auditory probe. Results support that mind wandering has an impact on driving performance and the associated change in driver’s attentional state is detectable in underlying brain physiology. Further, results suggest that detecting the internal cognitive state of humans is possible in a continuous task such as automobile driving. Identifying periods of likely mind wandering could serve as a useful research tool for assessment of driver attention, and could potentially lead to future in-vehicle safety countermeasures.

The Effects of Teen Passengers on Teen Driver Speeds and Headways

This observational study investigated teen driving as a function of passenger presence and passenger gender. Vehicles were observed leaving high school parking lots at dismissal time, and the apparent age (teen or adult) and gender of drivers and passengers were recorded. At sites near the school, vehicle speeds and headways were recorded using a LIDAR and video-based system. Vehicles in the traffic stream were matched, where possible, to vehicles identified leaving the school. Thus, vehicles driven by teens could be distinguished from “general traffic.” Passenger presence and gender had strong effects on speed and headway and were more pronounced than driver gender effects. While teens drove slightly faster than general traffic, the primary influence on speed was the presence of a male passenger. Similarly, shorter headways were associated with male, rather than female, passengers. Passenger influences on teen driving depend on passenger gender, driver gender, and the particular driving measure.

Safe Driving in the Multi-Tasking Generation

The objective of this discussion panel is to approach the teen driver distraction issue from the driver life-style point of view. As revealed in various focus groups and surveys, multi-tasking is “just what they do,” and what they have grown up doing. How (if at all) is the current generation of young drivers distinct in terms of multi-tasking? What are the implications and how might we deal with this? The approach here is to provide a multi-disciplinary panel that offers a range of expertise and perspectives on studying these issues. Each of five panelists will present a brief perspective of the problem from the point of view of their expertise. This will be followed by an open discussion period.

On-the-Road Driver Behavior Experimentation Issues and Approaches

This panel addresses a research methodology that is becoming more essential for driving safety research. The methods of driving simulation and naturalistic driving have been prominent and remain important, but their limitations are becoming more evident. On-the-road experimental methods offer some of the advantages of naturalistic driving while providing a degree of experimental control and manipulation more typical of simulator experiments. Five expert researchers will discuss both scientific and pragmatic issues in the conduct of on-the-road experimentation, making use of lessons learned from their own studies. Each panelist will present a brief perspective on the problem from the point of view of their experience and expertise. This will be followed by an open discussion period.

Effects of Multiple-Device Integration Strategies on Driver Comprehension of Crash Warnings

This experiment investigated the extent to which driver comprehension of imminent crash warnings is affected by the degree of integration when there are multiple Connected Vehicle products in the vehicle. Two displays were placed in an experimental vehicle: one representing original equipment and one representing a portable, nomadic device. Participants were randomly assigned to one of five device integration conditions. Participants drove on a test track and were occasionally presented with either a nonurgent message or an urgent crash warning. Participants recognized warnings most quickly when only one display was active in the car; when both displays were active, response times generally improved when messages and warnings were integrated into a single physical location. Warning recognition times were longer when a warning closely followed a non-urgent message on the other display than when a warning followed a non-urgent message on the same display. When messages and warnings from both source displays were integrated into a single display, this effect was not observed, suggesting that the separate display locations are responsible for the increased warning recognition time rather than the different formats of the messages from each source device.

A New Resource for Effective Consumer Product Instructions: Manufacturer's Guide to Developing Consumer Product Instructions:

This paper describes a new resource for developing and evaluating consumer product instructions. The U.S. Consumer Product Safety Commission (CPSC) staff, when conducting product safety assessments, often finds that the instructions provided with a product are deficient and result in consumers misassembling or misusing the product. Therefore, CPSC staff recently released the Manufacturers Guide to Developing Consumer Product Instructions. This Guide is unique in providing a relatively comprehensive, yet compact, set of principles specifically addressing the development and evaluation of instructional material for consumer products. It has a strong human factors orientation. The approach to developing the document was based upon the behavioral sequence that must be accomplished if the final outcome is to be a change in product user behavior. The content, structure, and perspective of the Guide make it useful for human factors professionals in product design, safety research, and forensics, as well as for developers of instructions and safety materials.