Transportation Research Record: Journal of the Transportation Research Board

Engaging in conversation diverts attention from cognitive processes associated with driving. Drivers tend to commit errors that may lead to crashes when their attention is focused away from the driving task. The interference occurs at the level of central attentional processes that are especially susceptible to aging. The current study assessed the effects of a controlled auditory—verbal processing load induced by the Paced Auditory Serial Addition Task (PASAT) on vehicle control by 160 legally licensed older drivers. Of these drivers, 78 were neurologically normal (mean age of 71 years) and 82 (mean age of 75 years) had impairments of selective attention but no diagnosable neurological disease. Measurements aboard the instrumented vehicle Automobile for Research in Ergonomics and Safety showed that performing the PASAT reduced speed and steering control of the older drivers relative to baseline (no-task) driving conditions and was associated with greater counts of at-fault safety errors. Yet, driving performance did not differ significantly between neurologically normal and attention-impaired older drivers between PASAT and no-PASAT (baseline) conditions. It may be that the PASAT, which involves auditory-verbal and working-memory, sustained-attention, and executive-function components, commands different resources than driving on uneventful highways, which might rely on overlearned, automatic cognitive processes. Interference produced by PASAT, like that of cell phone operation, might become more evident during demanding driving conditions, as exist at busy traffic intersections. Relevant studies in these potentially unsafe circumstances can be conducted in a driving simulator, as in our ongoing research on older drivers.

Cataracts are the main cause of reversible vision impairment in older adults. An investigation examined how cataracts and cataract surgery affected driving performance and determined whether any changes in driving performance could be predicted by self-reported perceptions of driving and vision. Twenty-eight older participants with bilateral cataracts and eighteen age-matched control participants with normal vision were tested. All were licensed drivers. Driving and vision performance were measured before cataract surgery, after first-eye surgery, and again after second-eye surgery for the cataract participants and on three separate occasions for the control group. Driving performance was assessed on a closed-road circuit. Visual acuity and contrast sensitivity were also measured at each test session. Self-perceptions of vision and driving were assessed with the Activities of Daily Vision Scale (ADVS). The participants with cataracts had significantly poorer (p <.05) driving performance at the first visit compared with the control participants for a range of measures of driving performance, which significantly improved to the level of the control participants following cataract extraction. Self-perceived changes in driving performance assessed with the ADVS were not strongly related to the actual changes in driving performance recorded. Together these findings indicate that participants with cataracts have poorer driving and vision performance than age-matched control participants and that cataract surgery can result in significant improvements in driving, which are not predicted by self-reported measures such as the ADVS.

A study investigated the effects on safety belt citations of the change in police enforcement of Michigan's mandatory safety belt law that went into effect on March 10,2000. Safety belt citation records were obtained from Michigan courts for one full year before and one full year after the change from secondary to standard enforcement. Analysis of the records indicated an overall increase of 9% in safety belt citations and an 8% increase in the number of individuals cited. No effects from the change to standard enforcement were found for the distribution of safety belt citations by sex, age, and race, overall, or for both day- and nighttime periods. The proportion of persons receiving multiple safety belt citations in one year remained at 11%, and the average number of citations per cited person remained at 1.1 per year. Individuals who continued to receive citations after standard enforcement were more likely to be males age 16 to 22. No effect on the number of child-restraint citations was found. Changes in the disposition of cases included an increase in the proportion of guilty outcomes and a decrease in the proportion of cases dismissed.

Statistics indicate that red-light running has become a significant safety problem throughout the United States. There is a wide range of potential countermeasures to the problem of red-light running; an increase in yellow duration is one countermeasure. The objective of this research was to quantify the effect of a change in yellow-interval duration on the frequency of red-light violations. A before-after study is described and the resulting data are used to quantify the effect of increasing the yellow interval on the frequency of red-light violations. Based on this research, it was concluded that (a) an increase of 1.0 s in yellow duration (such that it does not exceed 5.5 s) will decrease the frequency of red-light violations by at least 50%; (b) drivers do adapt to the increase in yellow duration, but this adaptation does not undo the benefit of an increase in yellow duration; and (c) increasing a yellow interval that is shorter than the value obtained from a proposed recommended equation published by the Institute of Transportation Engineers is likely to yield the greatest return (in terms of a reduced number of red-light violations) relative to the cost of retiming a yellow interval in the field.

A detailed statistical analysis is presented of the effects of speed limit enforcement cameras on injury accident numbers. The approach used is constructed in such a way that it is possible to differentiate not only between the effects of the cameras and the effects of trend and seasonality but actually to produce estimates that are independent of any other overall time-dependent effects. Crucially, the estimates produced are also net of the effects of regression to the mean. To allow for the simultaneous treatment of the different levels of severity, weights are used that reflect the frequency of the different types of accidents. This approach is then used on a data set for all injury accidents in Cambridgeshire between 1990 and 2002, which also contains data from 49 camera sites. To quantify the range of effectiveness of the cameras, estimates of the changes in accident numbers are produced for different distances from the camera site. The analysis shows that, overall, in the immediate vicinity of the camera sites, the installation of a camera can be expected to lead to decreases in weighted injury accident numbers by an astounding 45.74%. Lower, but still significant, decreases are observed in the wider surrounding area. Finally, to provide further insight into the differences in performance on different road types, the sites are grouped together according to road category. This analysis shows that the biggest reduction in accident numbers can be obtained on roads with a higher incidence of speeding offenses.

Introduced are the ideas found in the integrated safety management system (ISMSystem), published as National Cooperative Highway Research Program Report 501. The ISMSystem is founded upon the principle that aligning the activities of different agencies within a jurisdiction can result in a level of safety unobtainable by those agencies working independently and in decision-making isolation. In addition to providing highway safety benefits, implementing the ISMSystem should result in cost savings when the resources of different agencies are pooled and shared. The ISMSystem describes an organizational structure that includes a coalition of highway safety agencies that develops a common mission and vision at the highest level of management. Safety professionals with expertise in relevant emphasis areas are recruited into teams to address the specific goals set out by the coalition and in doing so produce action plans that integrate the activities of the implementing agencies. The integrated safety management process describes the process for going from crash data to integrated action plans to increase safety. A workshop introducing safety professionals to the ISMSystem and allowing multidisciplinary teams to practice developing strategies to address safety emphasis areas has been recently conducted in the state of Iowa. The key lessons from the Iowa workshop are summarized, including the need for setting quantifiable safety goals, the need for both horizontal and vertical agency integration, interaction among emphasis areas, and the types of issues the ISMSystem is designed to address.

Working with the North Carolina Department of Transportation, Municipal and School Traffic Assistance Program, a research team from the Institute for Transportation Research and Education at North Carolina State University studied the traffic at 20 elementary school campuses during the peak afternoon school-travel hours. Study results led to several observations and recommendations. On average, 60% of carpool vehicles arrived in the carpool lane before the afternoon school dismissal time and spend an average of triple the amount of time of those who arrived shortly after the bell-ring time. Establishing multiple loading bays and staffing each bay with safety patrol to assist loading can greatly reduce vehicle loading and unloading time. The act of loading and unloading students should take less than 10 s per vehicle; the complete process of a vehicle entering, loading and unloading passengers, and then exiting can be completed in less than 45 s. Limiting options for drivers will reduce circumventions that may lead to crashes. If spillage onto adjacent roadways is a problem, a double lane for the queue at some point in the carpool lane is a viable solution. School traffic congestion can be addressed by encouraging a mode shift from private vehicles to school bus transportation, walking, or biking. To convey the study results to school administrators and to illustrate recommendations, a website (www.itre.ncsu.edu/stg) was created; it contains a simple decision tree to assist administrators in identifying the nature of a traffic concern and to provide recommendations for appropriate solutions. It also illustrates schematics of the optimal layout for loading and unloading students, with explanations of the recommended operating procedures and video clips of actual operations.

The city of New Orleans is among the most vulnerable cities in the world to the threat of hurricanes. To protect its population from these storms, officials in Louisiana have joined a growing number of states that are planning to use contraflow freeway operations to expedite the evacuation of threatened areas. Although contraflow is widely regarded as a major advance in evacuation planning and response, no one really knows how well, or even if, it will work. Research was undertaken to improve the understanding of traffic conditions on contraflow freeway segments during an evacuation. The CORSIM microscopic traffic-simulation program was used to model the freeway configuration that will be used to evacuate New Orleans as well as two alternative scenarios for this same segment. The results showed that the currently proposed configuration might result in an underutilization of the contraflow segment, thus significantly limiting the number of evacuees who can get out of the city. The study also showed how the effectiveness of the New Orleans contraflow segment might be significantly improved with some simple and inexpensive modifications to the existing plan. Most important, the results of the research underscore the critical nature of proper planning and design of contraflow entry points and how they are often overlooked for both emergency and nonemergency conditions.

The Insurance Corporation of British Columbia (ICBC) has been involved in the investment of road infrastructure improvement for many years, delivering an annual program known as the Road Improvement Program. Corporation staff realized that selective road improvement projects have tremendous potential to improve road safety performance. This improved road safety performance, measured in terms of a reduction in the frequency and severity of collisions, also led to a reduction in the cost of automobile insurance claims. This reduced claim cost provided the basis for the economic justification for investments in road infrastructure improvements. To ensure that the justification for the ICBC investment in road safety improvements is verified, a formal evaluation of the Road Improvement Program is undertaken at regular intervals. However, conducting a thorough and reliable evaluation of road safety projects can be difficult and involves significant effort. Presented are details of the important factors that should be considered when conducting an evaluation of road safety improvement projects. The methodology and results used to perform the latest ICBC program evaluation are described.

Traffic crashes, injuries, and fatalities on roads and highways are of great concern to safety professionals in the United States. These problems are often caused by infrastructure inadequacies, increasing traffic, and inappropriate driver behavior. Reduction of traffic crashes and injuries is possible if an effective statewide safety-improvement program is implemented. Development of such a program requires careful investigation and analysis of historical traffic-crash data and use of an intelligent resource-allocation strategy. A statewide traffic-crash analysis was performed with crash and exposure data for the entire state of Michigan. Typically, the resources available for safety projects and programs are not sufficient to undertake a comprehensive set of safety initiatives for the entire state. Therefore, it is important that the available resources are used optimally to achieve the greatest overall safety benefits. The Office of Highway Safety Planning (OHSP), a division of the State Police Department of Michigan, provides funding to local governmental agencies for a variety of safety projects and programs to alleviate traffic crashes and injuries. Most of the projects funded by OHSP involve safety initiatives related to alcohol, the use of safety-restraint systems, enforcement of traffic regulations, and programs related to driver behavioral issues. A comprehensive analysis of traffic crashes and injuries was performed with the past five years' crash data for all 83 counties in the state of Michigan. The high-priority areas for implementing safety initiatives in the state were identified and prioritized through a safety performance index (SPI) developed as a part of this research. The SPI involves the use of historical crash data and multiple exposure variables. The development, analysis, benefits, and uses of SPI are described. Based on the SPI values, development of an optimal resource-allocation model using linear programming techniques is also presented.

The human circadian system is sensitive to environmental conditions, such as those created by shift work, that affect the timing and duration of sleep. Previous research on the effects of shift work, however, has focused primarily on regularly scheduled shifts. Few studies have focused on irregular and unpredictable on-call shift systems, such as those found in much of railroad operations. The purpose of the current study was to examine the effect of irregular shift systems experienced by locomotive engineers on the length of sleep-wake periods and the effect of different length sleep-wake periods on self-reported sleep quantity, sleep quality, and on-duty alertness. A total of 179 locomotive engineers provided information on work times, sleep habits, and on-duty alertness as part of a 14-day activity log. Sleep-wake periods were first divided into three categories: short (<22 h), normal (22 to 26 h, inclusive), and long (>26 h). A one-way analysis of variance for multiple variables was completed on sleep quantity, sleep quality, and on-duty alertness by using the three sleep-wake period categories as the factor. The results indicated that normal-length periods occurred in less than half of the sleep-wake periods. The remaining sleep-wake periods were divided approximately equally between short and long periods. In addition, short sleep-wake periods resulted in less sleep and generally poorer sleep than normal length sleep-wake periods. Long sleep-wake periods resulted in more sleep but poorer sleep and lower levels of on-duty alertness than normal sleep-wake periods. Furthermore, on-duty alertness followed a circadian rhythm with the most well defined rhythm seen in normal length sleep-wake periods and less pronounced rhythms seen in short and long sleep-wake periods. The current data indicated that the range of sleep-wake periods caused by irregular working conditions negatively impacted sleep habits and on-duty alertness in locomotive engineers.

The objective of this study was to assess the magnitude of overheight vehicle collisions with highway bridges that caused structural damage, injuries, and sometimes even fatalities at both the Maryland and the national levels. The seriousness of the collisions was exemplified by a case in 1999 in which a truck hauling an overheight excavator struck and collapsed a pedestrian bridge over the Baltimore Beltway, killing one motorist and injuring three others. Statistics on overheight collisions in Maryland were collected from overheight vehicle detector records, the statewide accident database, and bridge inspection reports. An analysis of the data revealed that the frequency of overheight accidents reported in Maryland increased by 81% between 1995 and 2000. Of the 1,496 bridges susceptible to impact by overheight vehicles statewide, 309 (20%) have been struck, with 58 (4%) having required repairs. No nationwide databases on overheight collisions exist, so a survey was sent to each state to collect national statistics. Of the 29 states responding, 18 (62%) indicated that they consider overheight collisions to be a significant problem, but few were able to provide hard data.

The incidence of freak weather and geological events, such as earthquakes and volcanic eruptions, has increased over the past 30 years. Coupled with an increase in the populations located in the path of these natural disasters, the imminent danger posed by naturally occurring phenomena has also risen. Given the potential dangers, it is wise for policy administrators to ensure that appropriate emergency plans are in place that aim to minimize the negative consequences associated with these disasters. Effective emergency planning and management should successfully combine the skills and knowledge of law enforcement agencies and transport planners as well as the knowledge and skills of emergency planning professionals. In Australia, there has not been a thorough investigation of the emergency impacts on the transport infrastructure nor have emergency plans adequately integrated the transportation aspect. Which transport routes evacuees and emergency vehicles should use is a question that needs to be answered urgently to avoid situations where evacuees are trapped in their vehicles; in which emergency personnel are unable to gain access to the people in need; and in which emergency vehicles are not able to get onto the road network due to traffic congestion. Thus, in a case of a suburban bushfire (wildfire), a fire that may have been easily extinguished or controlled is left to engulf more bushland and increase in ferocity. The many emergency evacuation models developed are critically assessed, and the important information required to devise the models is described. It is clear, however, that more research needs to be undertaken to investigate specifically the effects of a mass evacuation on current transport networks.