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CHAPTER 1 Introduction This report provides the final results of research on NCHRP Project 03-73, "Separation of Vehicles--Commercial Motor Vehicle (CMV)-Only Lanes." It presents a review and discussion of a wide range of issues relevant to planning, designing, and evaluating CMV-only lanes that should be useful to planners and policy-makers in the public and private sectors. It also presents results of a comparative evaluation of the performance of different CMV-only lane concepts, and potential benefits and costs of these concepts. Finally, it concludes with a discussion of potential areas of further research on promising CMV-only lane concepts. 1.1 Project Overview For a number of years, there has been growing interest in CMV-only lanes, and several notable proposals for CMV-only lane systems/projects have appeared in the planning and traffic engi- neering literature. To a large extent, this growth in interest has been related to the growth in truck traffic relative to automobile traffic and the contribution of truck traffic to congestion. Heavy trucks (standard trucks as well as longer combination vehicles [LCVs]) have a greater impact on capacity than their sheer volume would suggest, especially when mixed with auto- mobiles. Separation of autos and trucks may be a beneficial way of building more system capacity in certain circumstances. A number of studies also have suggested that CMV-only lanes that are tolled may present a viable means of financing system capacity improvements. The argument has been made that trucks have a higher value of time than autos, and may therefore be willing to pay a higher price for congestion relief. In addition to congestion relief, truckers might also be willing to pay tolls on CMV-only lanes that facilitate operations of LCVs and other oversize/overweight (OS/OW) trucks, in order to be able to engage in these operations to improve trucking productiv- ity and operational efficiency. A number of studies have shown that system reliability is especially critical in the movement of high-value, time-sensitive commodities, and that the reliability benefits of CMV-only lanes (due to the combination of less overall congestion and the incident-reduction potential of truck-auto separation) may provide added value for which truckers/shippers would be willing to pay. It also has been suggested that separation of autos and trucks may have significant safety benefits. Autos are far more maneuverable than heavy trucks, yet auto drivers often do not take this into account when making certain fast response driving maneuvers and this can lead to increased crashes. Fur- ther, when trucks and autos are involved in crashes, they are far more likely to be fatal crashes than when crashes involve only autos. The objectives of the Separation of Vehicles--CMV-Only Lanes Project are to compile data from actual applications and studies of emerging concepts and use these data to present a profile of the benefits and costs of CMV-only lanes. This information will serve as a reference guide for planners 1