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3BACKGROUND AND PROBLEM STATEMENT Speed limiters (also described as speed governors) are devices that interact with a truck engine to only permit the attainment of a pre-programmed maximum speed. They have been used in Europe and Australia for more than a decade to limit the speed of large trucks and are currently widely available in the United States on late model and new Class 8 trucks. Many 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 level optimum for these factors. From a safety perspective, the premise is that by slowing down large trucks the travel risks for all motorists may be lowered by reducing the number of collisions and mitigating the severity of those that do occur. The counter-argument is that safety can be compromised because speed-limited vehicles cannot accelerate to avoid traffic conflicts (e.g., in merging situations), and the slower speed of these vehicles relative to the surrounding traffic creates speed differentials that have been correlated with increased crash risk. As described in the body of this report, there is controversy within the trucking industry as to the safety effectiveness of speed limiters. This controversy has been heightened by an initiative to mandate the use of speed limiters in Ontario, as well as the other Canadian provinces, and the active advocacy of a speed limiter mandate in the United States by the ATA and other organizations. The NHTSA is currently evaluating responses to a Request for Comments on such a mandate. With this in mind, the CTBSSP initiated this project to 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 policy development in North America. This synthesis can also provide a foundation for further developments in the application of speed limiters to commercial vehicle operations. In addition to synthesizing previous studies, a convenience survey of trucking industry stakeholders was completed within the project to gain a qualitative view of speed limiter use, adverse consequences, and perceived effectiveness in safety, fuel efficiency, and tire wear. OBJECTIVES AND SCOPE The project scope encompasses studies assessing the safety effectiveness of speed limiters for commercial motor vehicles (CMVs) in Australia, Europe, and North America. The objec- tives of this synthesis are to document current knowledge and state of practice for speed limiters in commercial vehicle operations and to survey truck and intercity and charter bus carriers who have experience in using speed limiters regard- ing perceived benefits and/or drawbacks. The synthesis also identifies additional research needed to better understand key questions with regard to the safety benefits of speed limiters. APPROACH The first step in the study was an extensive literature review to identify previous studies on this topic. The results of the liter- ature review were assimilated to address the core question of what might be learned from such earlier work, as well as the methodology and validity of reported results. This process pro- vided a foundation for designing a survey of trucking industry professionals addressing key speed limiter issues. These tasks led to the formulation of conclusions and potential next steps. In early 2007, before the beginning of this CTBSSP proj- ect, the American Transportation Research Institute (ATRI) independently initiated a review of speed limiters, including a review of related safety studies and a survey of motor carriers. The synthesis team coordinated its efforts with ATRI and incorporated relevant information and survey results to maxi- mize commercial truck carrier response and avoid duplicative efforts (McDonald 2007). A further source of perspective and insight in the overall process was provided by reviews of the preliminary results by the TRB CTBSSP Program Panel. Literature Review The Study Team performed an extensive literature search to identify information available on the safety impacts of speed limiters installed on commercial vehicles and/or buses, empha- sizing commercial vehicle operations in North America, Europe, and Australia. A search process for the literature review was conducted using a variety of online databases and search engines. Major information sources for the literature review included: ⢠FMCSA research publications ⢠ATRI and other industry research and information publications CHAPTER ONE INTRODUCTION
⢠Traffic safety research literature (e.g., Accident Analysis & Prevention) ⢠Industrial safety management literature (Journal of Safety Research, Journal of Organizational Behavior Management, Professional Safety, Occupational Health & Safety) ⢠Proceedings of the American Society of Safety Engi- neers ⢠Proceedings of the Transportation Research Board ⢠Transportation Research Information System ⢠Trade publications ⢠Web pages relating to CMV transportation safety. In addition to these searches of academic literature and other publications, the synthesis team contacted government agencies (both foreign and domestic), as well as trade asso- ciations, state motor carrier organizations, and academic resources, seeking information on unpublished speed limiter studies. Specifically, they were queried as to past and current applications, programs, and studies involving the use of speed limiters; further, these contacts were asked to provide guid- ance on any other speed limiter safety effectiveness studies. See Appendix A for the full list of organizations contacted. Commercial Vehicle Industry Survey A survey targeting fleet safety managers was developed based on issues identified in the literature review with the core objective of gaining additional insight as to usage levels and perceived benefits and drawbacks of speed limiters from actual users. Several outside safety experts were included in the survey to gain additional perspective. The written survey was distributed by e-mail to approximately 1,500 individuals (including multiple safety managers within specific compa- nies), representing roughly 400 truck and motor coach fleets plus other industry stakeholders. As will be discussed in chapter three, the written survey addressed topics such as fleet size, type of fleet operation, use of speed limiters (number of vehicles, how long, etc.), opera- tional aspects (set top speeds, driver violations or tampering), fleet assessment of safety benefit, operational impacts (speed- ing citations, fuel savings, slower/fewer deliveries, etc.), driver response, and overall experience with speed limiters. The written survey was designed to collect core information and provide guidance on follow-up telephone interviews with a small number of select fleet safety personnel with detailed knowledge of speed limiters. The written survey results were analyzed to identify core speed limiter issues, which were the focus of the telephone surveys. For surveying fleet safety managers, the synthesis team fol- lowed the successful model used in prior CTBSSP studies by members of the synthesis team. The initial contacts included past CTBSSP survey respondents, who may be characterized 4 as safety-conscious fleet safety managers from many CMV transport operations types [e.g., truckload, less-than-truckload (LTL), and private]. Additional safety managers were identi- fied based on collected information and through industry con- tacts (i.e., trade associations and carrier contact lists provided by ATRI). To enhance the survey process, the respondents were offered a free copy of the project final report. This was seen as critical to obtaining an adequate respondent sample and also served the primary aim of the CTBSSPâto disseminate relevant findings and products and promote program visibil- ity within the CMV industry. ORGANIZATION OF THE REPORT Chapter one provides a brief overview of the project, includ- ing the problem statement, scope, objectives, and approach. The chapter also discusses a primary survey that targeted fleet safety managers to obtain additional insight as to usage levels and perceived benefits and drawbacks of speed lim- iters from actual users. Chapter two describes the findings of the literature review, including the assessment of prior published studies regarding speed limiter use, effectiveness, and legislation. Although sev- eral key findings are identified, the literature search revealed a paucity of relevant published research on how speed limiters directly affect safety and driving behavior. The most definitive results on the effectiveness of speed limiters comes from the United Kingdom, which showed that the crash involvement rate for speed-limited heavy trucks fell 26% between 1993 (when mandated) and 2005. U.K. authorities noted that other contributing factors may have influenced the decline, but con- cluded that speed limiters at least played a significant role. The chapter also proffers the advantages and disadvantages of speed limiters as described in the literature. Positive impacts primarily focus on safety and fuel efficiency. Concerns raised in the literature against using speed limiters include a lack of a consistent set speed across North America and the inabil- ity of a speed-limited vehicle to accelerate in risky traffic scenarios. Chapter two also reviews the current utilization of limiters from multiple-user and non-user perspectives. Industry per- spectives on using speed limiters were illuminated by two surveys found in the literature. An OOIDA Foundation (OwnerâOperators Independent Drivers Association) survey reported that more than 81% of respondents would rather drive for a company without speed limiters; with the driversâ primary concern with speed limiters being the lack of passing speed. An ATRI survey found overall installation rates of speed limiters at 63% for motor carriers, which are compa- rable to rates identified in the OOIDA study. ATRI found it difficult to meaningfully compare fleet safety data before and after speed limiter installation owing to the small number of carriers that provided empirical safety data.
5Chapter three presents the results of the Study Teamâs primary survey and interviews with key safety managers. The survey addressed topics such as fleet size, type of fleet opera- tion, use of speed limiters, operational aspects (set top speeds, driver violations or tampering), fleet assessment of safety benefit, operational impacts (speeding citations, fuel savings, slower or fewer deliveries, etc.), driver response, and over- all experience with speed limiters. Note the response rate of the current survey was approximately 7% (103 of 1,500 fleet safety managers completed the survey). The survey can best be described as a small population convenience survey of the commercial motor vehicle industry; as such, the results should not be considered definitive and should be inter- preted with this in mind. It is not known whether the survey responses are representative of the overall trucking and motor coach industry. Chapter four draws conclusions from the results, identi- fies gaps in our current knowledge, and offers potential steps for future research initiatives. The current synthesis pro- vides a preliminary understanding of speed limiter use in CMV operations; it does not provide, however, a method- ological comparison of before and after results applied uni- formly across predefined truck and bus fleet operations. This final chapter outlines an approach to an in-depth empirical study that would harvest data from the commercial truck and bus industry with regard to the safety effectiveness of speed limiters.
