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3 CHAPTER ONE INTRODUCTION BACKGROUND AND PROBLEM STATEMENT (CMVs) in Australia, Europe, and North America. The objec- tives of this synthesis are to document current knowledge and Speed limiters (also described as speed governors) are devices state of practice for speed limiters in commercial vehicle that interact with a truck engine to only permit the attainment operations and to survey truck and intercity and charter bus of a pre-programmed maximum speed. They have been used carriers who have experience in using speed limiters regard- in Europe and Australia for more than a decade to limit the ing perceived benefits and/or drawbacks. The synthesis also speed of large trucks and are currently widely available in the identifies additional research needed to better understand key United States on late model and new Class 8 trucks. Many questions with regard to the safety benefits of speed limiters. truck fleets use speed limiters for their safety contribution as well as to reduce fuel use and tire wear, with the speed set at a APPROACH level optimum for these factors. The first step in the study was an extensive literature review to From a safety perspective, the premise is that by slowing identify previous studies on this topic. The results of the liter- down large trucks the travel risks for all motorists may be ature review were assimilated to address the core question of lowered by reducing the number of collisions and mitigating what might be learned from such earlier work, as well as the the severity of those that do occur. The counter-argument is methodology and validity of reported results. This process pro- that safety can be compromised because speed-limited vehicles vided a foundation for designing a survey of trucking industry cannot accelerate to avoid traffic conflicts (e.g., in merging professionals addressing key speed limiter issues. These tasks situations), and the slower speed of these vehicles relative to led to the formulation of conclusions and potential next steps. the surrounding traffic creates speed differentials that have been correlated with increased crash risk. In early 2007, before the beginning of this CTBSSP proj- ect, the American Transportation Research Institute (ATRI) As described in the body of this report, there is controversy independently initiated a review of speed limiters, including a within the trucking industry as to the safety effectiveness of review of related safety studies and a survey of motor carriers. speed limiters. This controversy has been heightened by an The synthesis team coordinated its efforts with ATRI and initiative to mandate the use of speed limiters in Ontario, as incorporated relevant information and survey results to maxi- well as the other Canadian provinces, and the active advocacy mize commercial truck carrier response and avoid duplicative of a speed limiter mandate in the United States by the ATA efforts (McDonald 2007). and other organizations. The NHTSA is currently evaluating responses to a Request for Comments on such a mandate. A further source of perspective and insight in the overall process was provided by reviews of the preliminary results With this in mind, the CTBSSP initiated this project to by the TRB CTBSSP Program Panel. synthesize data, research, and analyses performed to date in terms of both the methodologies employed to assess speed limiters and the actual results, which may be used to guide Literature Review policy development in North America. This synthesis can The Study Team performed an extensive literature search to also provide a foundation for further developments in the identify information available on the safety impacts of speed application of speed limiters to commercial vehicle operations. limiters installed on commercial vehicles and/or buses, empha- In addition to synthesizing previous studies, a convenience sizing commercial vehicle operations in North America, survey of trucking industry stakeholders was completed within Europe, and Australia. the project to gain a qualitative view of speed limiter use, adverse consequences, and perceived effectiveness in safety, A search process for the literature review was conducted fuel efficiency, and tire wear. using a variety of online databases and search engines. Major information sources for the literature review included: OBJECTIVES AND SCOPE · FMCSA research publications The project scope encompasses studies assessing the safety · ATRI and other industry research and information effectiveness of speed limiters for commercial motor vehicles publications