John Woodrooffe

Determination of Events Leading to Sport Utility Vehicle Rollover

To determine the major event pathways that result in sport utility vehicle (SUV) rollover, researchers at the University of Michigan Transportation Research Institute examined SUV rollover cases selected from the National Automotive Sampling System crashworthiness data system files for 1999 to 2001. Selected SUVs included the Ford Explorer, Jeep Cherokee, Chevrolet Blazer, Toyota 4-Runner, and GMC Jimmy for model years 1989 to 2001. Researchers coded up to six pre-rollover events, along with the stability of the vehicle (tracking or skidding) after each event. In addition, crash avoidance and recovery maneuvers were recorded, along with the rollover initiation type, location of rollover initiation, direction of roll, number of quarter turns of roll, location of roll, and surface condition at rollover initiation. Approximately 34% of SUV rollovers began with a loss of control caused by tire saturation, and about 75 % of the loss-of-control cases were on icy, wet, or snowy roads. Of the SUVs that ran off the road as the first event, 47% returned to the road before rolling over, and of these, 76% were tracking (presumed under control) before initial road departure. Between 40% and 49% of SUV rollover crashes experienced yaw instability while still on the roadway before roll. These rollovers may be addressed by electronic stability control devices if such devices can increase the control limits of the vehicle.

Prevention of Tractor–Semitrailer Rollovers: Effectiveness of Electronic Stability Control Systems

This study estimated the effectiveness of electronic stability control systems and roll stability control systems in preventing rollovers of heavy-truck tractor–semitrailers. The study combined hardware-in-the-loop simulation with the analysis of independent crash data sets. Engineering and statistical techniques were used to estimate the probable safety benefits of stability control technologies for five-axle tractor–semitrailers. The conventional approach for assessing the safety benefits of vehicle technologies was to analyze crash data sets containing data on the safety performance of vehicles equipped with the technology of interest. Because the deployment of the stability technologies for large trucks was in its infancy, national crash databases did not yet have a sufficient amount of factual data that could be directly linked to the performance of the technologies. Therefore a novel method of examining the potential benefits of these systems was used. This study focused on untripped vehicle rollovers in curves through the examination of crash scenarios that would be likely to benefit from the technologies; the probable effectiveness of each technology was estimated. The analysis in this study did not have the advantage of examining representative crash data sets that contained identifiable data from vehicles equipped with the technologies. Therefore, the analysis was based on probable outcome estimates derived from hardware-in-the-loop simulation, field test experience, and expert panel assessment, and these methods were used to estimate the safety benefits from the national crash data population.

Performance-Based Oversize and Overweight Permitting System

This paper presents a conceptual framework for a federally supervised, state-administered, performance-based oversize and overweight permit program for the operation of heavier and larger vehicles on the public highways. The structure of the permitting system is based on experiences and practices in implementing performance-based systems in Australia, Canada, New Zealand, and the United States. Conceptually, the framework consists of three main interrelated components: administrative, enforcement, and evaluation systems. The administrative system comprises several elements directed at establishing the requirements, standards, and administration of the permitting system. The enforcement system includes regulations, special conditions, education or communication to the industry, effective fines or penalties for violators, and adjudication. The enforcement system will periodically generate records indicating carrier compliance or noncompliance with the terms and conditions of permits and the frequency of these events. The evaluation system defines the data and processes to ensure that the permitting system is continuously evaluated. The results of the evaluation are necessary for revising the performance standards, limits, and conditions for the permitted vehicles. The challenge is enforcement of the performance-based, oversize and overweight permitting system. Periodic reassessments of permitted vehicles in addition to continued roadside enforcement of operating conditions are recommended.

Truck Productivity, Efficiency, Energy Use, and Carbon Dioxide Output: Benchmarking of International Performance

The Joint Transport Research Centre of the Organisation for Economic Co-operation and Development and the International Transport Forum recently conducted a benchmarking study of the safety and productivity of typical highway transport trucks from various countries. This paper focuses on vehicle productivity and efficiency in regard to the movement of freight. Forty vehicles from 10 countries were examined. The vehicles were designed for longer-haul applications and were classified in three separate categories: workhorse vehicles, which are the most common and can travel on most roads; high-capacity vehicles, which may be restricted to a certain class of road; and very high-capacity vehicles, which may be restricted to specific highways or routes. The metrics used in the analysis include maximum cargo mass and volume capacity, optimum cargo density, fuel consumption, and carbon dioxide output as a function of the freight task. The study found that size and weight regulations have a significant effect on the productivity and efficiency of heavy vehicles, including fuel consumption and vehicle emissions per unit of cargo transported. Significant variations were found among the vehicles from participating countries as well as within vehicle classes. It was also apparent that, in general, higher-productivity vehicles are correlated more strongly with increased cargo volume than with increased cargo mass and that larger trucks are better suited to lower-density freight than are workhorse vehicles. The study also found that it is important to consider the freight task when evaluating vehicle fuel consumption and emissions.

Opportunity Cost for Society Related to U.S. Truck Size and Weight Regulation: Freight Efficiency

Improvements in truck freight efficiency through such measures as optimized logistics and truck loading, the utilization of other transportation modes, and the reform of federal truck size and weight policy are expected to require fewer truck trips to move the nation’s freight. This reduction in truck travel distance should bring with it reductions in fuel consumption, emissions, and casualties as a result of reduced exposure. This paper discusses truck size and weight policy domestically and internationally and contrasts U.S. mass efficiency with that of the country’s North American Free Trade Agreement partners and, more broadly, with countries outside of North America. The analysis reveals the outdated nature of U.S. federal size and weight policy compared with other nations. The inability of U.S. federal policy to remain current with other countries is a result of a freeze on policy change that has been in place since 1982. An analysis of the societal benefits associated with improvements in truck freight efficiency is provided. Rather than estimating the precise benefits associated with the many options available, the analysis examines the benefits associated with a 10% reduction in truck travel distance. In this way, the paper provides insight into the significance of improved freight efficiency that reduces total truck travel distance, which in turn provides fuel savings, a reduction in emissions, and a reduction in truck crash frequency. The analysis concludes that a 10% reduction in truck distance traveled for a fixed national freight task would generate approximately

Safety Benefits of Stability Control Systems for Motorcoach Buses

16 billion, save 330 lives, and prevent approximately 4,000 injuries per year.

Roadside Alligators and the UMTRI Tire Debris Survey

The potential safety benefits of electronic stability control (ESC) systems for motorcoach buses operating within the United States are analyzed. “Motorcoaches” are defined as flat-front, high-platform buses equipped for intercity or long-distance travel. In recent years, ESC has increasingly become available as standard or optional equipment on motorcoaches. However, national crash databases do not include information that can be used to identify ESC-equipped buses. Moreover, even if the buses could be identified, the number of cases in available crash data is not sufficient to evaluate the safety performance of the technology in its current stage of deployment, particularly given the low number of motorcoach crashes. In light of these limitations, all recent fatal motorcoach crashes were examined by using information from the accident reports, formal studies of the National Transportation Safety Board, and information in reconstruction reports to estimate the likelihood that the crash could have been prevented or mitigated had the motorcoach been fitted with functioning ESC technology. Results indicate that, if it is assumed that ESC had been fitted to all motorcoach buses, annual savings of

Trucks involved in fatal accidents factbook 2002

25 million could have been realized from loss-of-control and rollover crashes prevented. Even though the financial benefits for motorcoaches are limited because loss-of-control crash events are rare, the nonmonetary value of this technology is likely to exceed the financial benefits because motorcoaches transport the public and the reasonable expectation is that effective safety technology should be used even if the exposure is low. In particular, the risk of passenger casualties in a high-speed crash is much greater for a motorcoach than for other vehicles because of the large number of people on board.

The Effectiveness of Electronic Stability Control on Motor Vehicle Crash Prevention

Roadside alligators (also known as tire debris) are those unsightly shreds or fragments of rubber occasionally found on the nations highways. The typical road user misunderstands the nature, extent, and contributing factors precipitating their formation. During the summer of 2007, the University of Michigan Transportation Research Institute conducted a national tire debris survey that involved the collection of 85,000 pounds of rubber and that provided 300 casings and 1,196 debris items for subsequent failure analysis. This paper discusses tire debris within the context of roadside litter, presents the tire debris survey methodology, and discusses the survey results. Overall, where the original equipment tread or retread status could be determined, original equipment accounted for 60%, and retreads accounted for 40% of the tire casings tested. For tire fragments, the status was 21% (original equipment) and 79% (retread). There was also a strong similarity for these same tire items in the ranking of probable causes of damage or failure. Road hazard or maintenance and operational factors were two of the top three probable causes of damage or failure. This result suggests that the majority of tire debris items found on the nations highways is not a result of manufacturing or process deficiencies. However, two primary challenges remain: first, increasing public awareness about the origins, characteristics, and impacts of tire debris and, second, ensuring adherence to the highest standards in commercial driver truck operations and associated tire maintenance. Resolving these challenges can significantly reduce roadside tire debris and correct the understanding of highway users about the origins of the roadside alligator.