Alison Smiley

THE ROLE OF EXPOSURE IN COMPARISONS OF CRASH RISK AMONG DIFFERENT DRIVERS AND DRIVING ENVIRONMENTS

Crash rates based on drivers, driver-kilometers, and driver-days in the denominator were compared, using survey estimates of time and distance driven and the annual frequency of traffic crashes in Ontario. Rates by age, sex, and region were computed for all crashes and for crashes resulting in injury or fatality. Young male drivers remained at high risk for all types of denominator; older women had high rates when distance was included in the denominator. When time spent driving was substituted, men and women drivers over 60 had very similar rates. For comparisons of rural residents with urban and northern residents, time and distance give equivalent results. These findings suggest that apparent differences in crash risk per kilometre, whether for older women or for urban drivers, is explained by differences in typical driving speed and environment. Exposure time is better than distance to explain crash risk among drivers and regions with very different driving patterns and environments.

Time vs distance as measures of exposure in driving surveys

A survey of drivers carried out in Ontario in 1988 has provided data on time spent driving as well as the distances driven for licensed drivers of both sexes in six age groups and three regions. Substantial differences were found in times, distances, and distance/time ratios among these groups. Men drove 50% greater distances, but spent only 30% more time driving than women; speed, averaged over each days driving, was lower for older drivers than for younger drivers. Differences in speed reflect differences in the driving done in urban or rural areas, and differences in the opportunity for road crashes; such differences, whether based on units of time or distance, will also affect both the comparisons of accident rates and the perceptions of risk among different groups of drivers. A definition of exposure to risk of road crash is required that considers both time and distance appropriately.

OBSERVED DRIVER GLANCE BEHAVIOR AT ROADSIDE ADVERTISING SIGNS

Express routes in North America are becoming more crowded, both in traffic density and in visual clutter. Higher demand for driver attention is a possible concern for regulators. Advertising signs add to this demand on visual attention. This study focused on the glance behavior of 25 drivers at various advertising signs along an expressway in Toronto, Ontario, Canada. The average duration of the glances for the subjects was 0.57 s [standard deviation (SD) = 0.41], and in total there was an average of 35.6 glances per subject (SD = 26.4). Active signs that contained movable displays or components made up 51% of the signs and received significantly more glances (69% of all glances and 78% of long glances). The number of glances was significantly lower for passive signs (0.64 glances per subject per sign) than for active signs (greater than 1.31 glances per subject per sign). The number of long glances was also greater for active signs than for passive signs. Sign placement in the visual field may be critical to a sign being noticed or not. Empirical information is provided to assist regulatory agencies in setting policy on commercial signing.

Behavioral Adaptation, Safety, and Intelligent Transportation Systems

It is intrinsic to human nature to modify behavior to suit new conditions. How drivers are likely to change the way they drive if their vehicles are equipped with intelligent transportation system (ITS) devices is considered. It is clear from the antilock braking system experience that improvements in safety cannot be predicted on the basis of proof-of-concept studies alone, in which one simply looks at changes in performance of the task being aided, whether that is braking, navigation, or detection of hazards. One also must look at changes in other aspects of the driving task and at the type of driving being done to determine the likely effect on safety. In particular, one should assume that there may be trade-offs of mobility for safety, that is, more driving in more difficult conditions and at higher speeds leading to more crashes. Further, one should expect drivers to attempt to increase productivity while driving, given reduced driving task demand. The prolific use of cellular phones is evidence of this behavior. Research is needed on driver mental models of ITS devices, to ensure that drivers understand how they function. The best design from a mechanistic point of view may not be the most effective for drivers.

Traffic Safety Evaluation of Video Advertising Signs

Road authorities are under increasing pressure from advertisers to allow video advertising in the right-of-way but are understandably concerned about whether video signs constitute a driving hazard. At the City of Torontos request, a comprehensive assessment of traffic safety impacts related to such signs was carried out in a series of studies involving three downtown intersections and an urban expressway site. An on-road eye fixation study was carried out to determine if drivers look at video advertising signs. Conflict studies were conducted to determine if there were more conflicts on intersection approaches with visible video signs than on those without such signs. A before-and-after sign installation study of headways and speeds on the urban expressway was carried out. Crashes were compared before and after sign installation at the expressway and three intersection sites. Finally, a public survey was conducted to determine if video advertising was perceived to affect traffic safety. On the basis of ...

Impact of video advertising on driver fixation patterns

To assess driver distraction because of video advertising signs, eye fixation data were collected from subjects who passed four video advertising signs, three at downtown intersections and one on an urban expressway. On average, drivers glanced at the signs on 45% of the occasions on which the signs were present. When drivers looked, they made 1.9 glances, on average, with an average duration per glance of 0.48 s. The distribution of eye fixations on intersection approaches where video signs were visible was compared with that on approaches on which video signs were not visible. No significant differences were found in the number of glances made at traffic signals or street signs. On the video approach, a greater proportion of glances were made at the speedometer and rearview mirrors. Glances were made at short headways and occasionally in unsafe circumstances. In the downtown area, glances at static commercial signs were made at larger angles and at shorter headways than was the case for video signs. A comparison of the results with those of other studies showed that video signs were less likely to be looked at than traffic signs (about half the time versus virtually every time, respectively) and that individual average glance durations and total durations were similar to those found for traffic signs in rural environments. These results apply to particular video signs in particular environments. Another on-road study indicates that a video sign on a curve that is close to the line of sight and visible for an extensive period is particularly distracting.

IDENTIFYING GAPS IN CHILD PEDESTRIAN SAFETY: COMPARING WHAT CHILDREN DO WITH WHAT PARENTS TEACH

Vehicle/pedestrian conflicts are a primary cause of deaths among children age 5 to 12 in North America. Children under 14 are twice as likely as the general population to be involved in vehicle/pedestrian accidents. Parents may overestimate the cognitive abilities of children to handle complex traffic situations and may assume that pedestrian rules taught to children at a young age will help safeguard them when crossing independently. For this reason, parental guidance on crossing safety was compared to actual practice by children, with and without accompanying parents or baby-sitters. Investigations were conducted in Kitchener-Waterloo, Ontario, a midsize, urban community. Interviews were done of a small sample (30) of well-educated parents in the vicinity of facilities used by children. Their responses were compared with observations of children (208) crossing at signalized and nonsignalized intersections in the same areas. While a high proportion of parents, 87 percent, teach safety practices, and 70 percent restate them when crossing with their children, 20 percent do not make unobserved checks of their children. Of those parents who do make unobserved checks, 42 percent found that none of their safety rules were being followed. Observations of children, not necessarily related to the adults interviewed, found that children were less likely to search for traffic at signalized than at nonsignalized intersections (p < 0.05). At nonsignalized intersections, 33 percent of unaccompanied children performed no visual search before crossing, increasing to 48 percent at signalized intersections. Even smaller numbers (< 6 percent) of unaccompanied children looked behind them for turning vehicles. These findings suggest that, while more research is needed to improve parental training and child response, more emphasis should be placed on responsibilities of drivers and on countermeasures in the traffic environment.

Evaluation of Prototype Highway Tourist Signs for Ontario

Information load and comprehension of new tourist signs for Ontario highways were evaluated. In a laboratory study involving 288 subjects, drivers searched for target destinations on timed sequences of slides of signs and identified whether their target was present, and, if so, its direction and distance. Performance was assessed in relation to number of names, number of signs in a sequence, arrow shapes, pictograph effectiveness, and sign organization. Signs used a letter height of 19 cm (7.5 in.). Subjects were allowed reading time equivalent to that available to drivers driving at 80 km/h (50 mph), who must time-share sign reading and vehicle control tasks. The results showed that with four or five names per sign, approximately one in eight subjects reported an incorrect direction for their target destination. Thus, a maximum of three names per sign was recommended. Results showed that a 70-degree chevron was as effective as a gerber arrow, that the number of signs in a sequence (two, three, or four) did not affect performance, and that having left followed by right destinations on a single sign resulted in equivalent performance to signs with left and right destinations on separate signs. The presence of pictographs increased the number of incorrect responses. Comprehension of 11 pictographs was assessed for 150 subjects. For 5 of 11 pictographs, comprehension was less than 85 percent.

Factors Contributing to Median Encroachments and Cross-Median Crashes

Previous studies of contributory factors associated with cross-median crashes have typically focused on median width and average daily traffic (ADT). A few studies have looked at the influence of geometry and cross-sectional elements. These studies did not explore many other design and operational factors that may contribute to cross-median crash frequency or severity (e.g., interchange ramps, interchange spacing, mixture of vehicle types, peak-period volumes, peak-period duration, land use, access control, driver workload, posted speed, or presence of speed transition zones). All median-related incidents begin with a median encroachment. Reducing median encroachments will reduce both cross-median crashes and fixed-object crashes in the median. Consequently, analyzing median encroachments should provide additional insight into the causes of cross-median crashes. There is also a knowledge gap regarding countermeasures appropriate for the various factors contributing to median encroachments and cross-median crashes. Although installing a barrier will greatly reduce cross-median crashes, it will also increase fixed-object crashes and the crash risk of maintenance personnel. Other countermeasures besides barriers exist, and knowing which ones effectively address the contributory factors on a highway will allow an engineer to develop a more effective design. This report identifies design and operational factors that contribute to the frequency and severity of median encroachments and cross-median crashes. It also identifies countermeasures for addressing those contributory factors. For this project, the research team reviewed the literature on median encroachments and cross-median crashes. Based on a survey of states, Canadian provinces, and turnpike/toll road authorities, the team compiled a list of design and operational factors likely to contribute to median encroachments and cross-median crashes. The research team then collected data to determine the relative contribution of each of the factors to median encroachments and cross-median crashes. Appendix D of the report provides recommended guidelines for reducing the frequency and severity of median-related crashes. This material is designed to be easily incorporated into a transportation agency’s design manual.

The Effects of Cellular Phone Use on Novice and Experienced Driver Performance: An On-Road Study

The purpose of this study was to examine the effect of cell phone use on novice as compared to experienced drivers to determine if a cell phone prohibition might be an appropriate graduated licensing restriction. Nineteen novices and twenty experienced drivers participated. The test route consisted of two laps around a 20-minute circuit and included a mixture of residential and urban roadways with speeds of 50 km/h or less. Participants drove an instrumented vehicle, made two outgoing calls, and received two calls during the course of the trip. For reasons of safety, participants were accompanied both by a researcher, and by a driving instructor with access to a second brake. With respect to the effects of experience on driving, no measures produced significant results. With respect to the effects of cell phone use on driving performance, two of six measures showed a trend, and one a significant difference between the call and no call condition; participants reduced their speed by a small, but significant amount, (1.27 km/h) during calls. The act of talking on the phone increases mental workload and information processing demands. The finding of effects on driver performance related to being on a call, and the lack of effects relating to experience differences, suggests that cell phone prohibition is appropriate for all drivers, not only novice drivers.