Bus and Rail Transit Preferential Treatments in Mixed Traffic
Transit preferential treatments are a key component to the provision of travel time savings and improved on-time performance for bus and rail systems operating in mixed traffic on urban streets. Rail systems operating on-street include both light rail transit and streetcar. Enhanced bus operations where transit preferential treatments are particularly critical include bus rapid transit and express bus.
Although transit preferential treatments on urban streets have been presented and reviewed with respect to their application and impact in several documents over the years there has not been a single, recent document that has addressed all of the potential treatments that have been or could be applied. This synthesis report provides such a document. Treat•ments that are addressed relate to both roadway segments and spot locations (intersections) and include the following:
- Roadway Segments
- Median transitway,
- Exclusive lanes outside the median area, and
- Limited stop spacing/stop consolidation.
- Spot Locations (Intersections)
- Transit signal priority (TSP),
- Special signal phasing,
- Queue jump and bypass lanes, and
- Curb extensions.
This synthesis report describes these different treatments and reviews their application, costs, and impacts. Three sources of information have been used: (1) a literature review (more than 20 documents), (2) a transit and traffic agency survey, and (3) selected case studies in four urban areas [San Francisco, Seattle, Portland (Oregon), and Denver].
The transit/traffic agency survey was sent to organizations contacted in 80 urban areas in the United States and Canada, 30 systems operating bus and light rail and/or streetcars on urban streets, and another 50 systems with just bus operations. Fifty-two agencies responded to the survey and provided the following insights:
- TSP is the most popular preferential treatment on urban streets.
- There are no standard warrants being applied to identify the need for particular treatments.
- Most transit agencies do not have formal comprehensive transit preferential treatment programs.
- Only a slight majority of transit agencies have intergovernmental agreements with traffic engineering jurisdictions in their service area related to developing and operating pref•erential treatments.
- Transit agency involvement in preferential treatments has focused on identifying, locating, and designing treatments, with construction and maintenance primarily left to the roadway/ traffic jurisdictions.
Twelve traffic engineering jurisdictions provided added insights from their perspective related to transit preferential treatments. These agencies conﬁrmed a focus on constructing and maintaining transit preferential treatments. They also noted that they were most supportive of TSP, queue jump/bypass lanes, exclusive lanes and limited transit stops, and least supportive of median transitways, special signal phasing, and curb extensions.
Including the transit and traffic agency responses (64 total), an 80% survey response rate was achieved related to the 80 urban areas contacted. In addition, insights were obtained from agency staff participating in the follow-up case studies.
The four case studies reviewed present a variety of transit preferential treatment applica•tions on urban streets. This included a comprehensive treatment program that has been in place for more than 30 years in San Francisco, related to both bus and light rail and streetcar operations, where TSP, exclusive lanes, boarding islands, and curb extensions have been applied at more than 400 locations in the city, and where the implementation process has been simpliﬁed over the years with the merger of transit operations and traffic engineering into the same agency. In Seattle, a similar comprehensive transit preferential treatment program has been implemented, but is just related to bus operations. King County Metro, the major bus transit operator in the Seattle area, has entered into multiple intergovernmental agreements with local cities to implement its TSP program. In Portland, the focus has also been on TSP applications with an intergovernmental agreement between Tri-Met, the public transit agency, and the city of Portland. In Denver, the cornerstone transit preferential treatment has been the development of the 16th Street Transit Mall, with associated limited stop improvements on adjacent downtown streets.
From a review of the literature, responses to the transit and traffic agency surveys, and the case studies, the capital and operating costs of different transit preferential treatments have been identified, including a set of unit costs, where possible, including appropriate ranges. The impact of different treatments on transit travel savings and improved on-time performance has also been identiﬁed. The analysis revealed that the greatest positive impact on transit operations is achieved through a systematic application of one or more preferential treatments along a corridor, with median transitways, exclusive lanes, and TSP having the greatest beneﬁt.
The synthesis report also presents a set of analysis methods to evaluate the travel time impacts of exclusive transit lanes, TSP, and queue jump/bypass lanes. This includes the use of ﬁeld sur•veys, analytical models (including a set of simpliﬁed nomographs), and simulation. A potential methodology to assess the cumulative impacts of a set of transit preferential treatments in a cor•ridor is also presented. Finally, decision frameworks are presented related to exclusive lanes, TSP, queue jump/bypass lanes, and curb extensions, to provide guidance to agencies on which preferential treatment might be most applicable in a particular location.
In concluding the synthesis assessment, ﬁve major areas for potential added research have been identiﬁed:
- Limited stop/stop consolidation impacts.
- Warrants for transit preferential treatment application.
- Beneﬁts of multiple transit preferential treatment application.
- Tradeoffs on intersection-based transit preferential treatments.
- Intergovernmental relationships in transit preferential treatment development.