This report contains guidelines for estimating bus lane capacities and speeds along arterial streets. It recommends level-of-service thresholds for buses based on speed, and it presents procedures for estimating the speed of buses using dedicated bus lanes on arterial streets. The capacity of a bus lane, where buses must follow each other without passing, is well established. There was relatively little information, however, on the bus flow capacity of an arterial that has an exclusive bus lane where buses have partial or exclusive use (i.e., dual bus lanes) of the adjacent lane. The level of service (LOS) of these bus facilities and their impact on arterial flow is not addressed in the current edition of the Highway Capacity Manual (HCM). Currently, bus impacts are addressed independently in Chapter 9, Signalised Intersections, and in Chapter 12, Transit Capacity, and not at all in Chapter 11, Urban and Suburban Arterials. A comprehensive and consistent procedure for assessing bus flow capacity and LOS, and the impacts of bus flow on arterials was needed. Under NCTRP Project 55-2 and TCRP Project A-7, Wilbur Smith Associates/Herbert S. Levinson developed speed thresholds for determining LOS and revised them based on comments from transit agencies, reviewed available analysis techniques, and developed new analysis procedures based on simulation and limited field data. These procedures can be used to determine the capacity and speed of bus flow on arterials with at least one exclusive lane for buses, with either no, partial, or exclusive use of the adjacent lane. Both procedures reflect delays due to traffic signals and dwell times. The procedures developed in this project are expected to be incorporated into the Year 2000 edition of the HCM and the Transit Capacity and Quality of Service Manual, which is the subject of TCRP Project A-15. (A)
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