The Transit Capacity and Quality of Service Manual (TCQSM) lists the following factors as influencing reliability: traffic conditions and road construction; vehicle and maintenance quality; vehicle and staff availability; transit preferential treatments; schedule achievability; evenness of passenger demand; variations in bus operator experience; wheelchair lift and ramp usage; route length and the number of stops; and operations control strategies. Weather—particularly snow and extreme temperatures—also plays a role. These factors have been addressed individually by research to some degree—for example, operations control strategies, scheduling, bus operator experience, route length, and applications of Automatic Vehicle Location and other technologies—but there is no comprehensive research that addresses all these factors in combination. Bus service reliability is a key quality-of-service issue for passengers, an important driver of bus operations costs for transit agencies, and a health and safety issue for bus operators. From the passenger point of view, unreliable service means that customers must allow extra time for their trip to make sure they arrive at their destination by a particular time—minimizing lost time that could otherwise have been used more productively. Although a typical rule of thumb is that passengers perceive wait time as being twice as onerous as in-vehicle time, recent research indicates that transit passengers perceive unexpected wait time as being 3 to 5 times as onerous as in-vehicle time. In contrast, automobile travelers value travel time unreliability (i.e., unexpected delay) at approximately the same level that they value travel time, suggesting that transit service is at a competitive disadvantage with the automobile with respect to unreliable travel times. From the transit agency point of view, travel time variability impacts a route’s cycle time and, ultimately, operating cost. Poor reliability (or unreliability) can increase labor costs. In a best-case scenario, reduced cycle time resulting from reduced travel time variability allows a bus to be removed from a route while maintaining scheduled headways. Conversely, if reliability issues are not addressed, a transit agency eventually needs to add buses to a route (increasing costs) or decrease bus frequency. From the bus operator point of view, unreliable service can lead to adverse effects such as increased assaults, operator fatigue, and fewer opportunities to use facilities. This condition may result in lost time, directly affecting operator availability and, ultimately, service reliability. Research is needed to develop guidance on measuring and valuing (a) reliability from the passenger, operator, and agency points of view; (b) the effects of potential operational, technological, and physical measures to improve reliability in particular situations; and (c) the potential benefits and costs of those actions. Accurately estimating the benefits of reliability-improvement measures is necessary for transit agencies, both to gain the acceptance of roadway-owning agencies to implement certain treatments (e.g., bus stop relocation or removal, traffic signal priority, queue jumps, street maintenance) and to compete for scarce transportation funds to implement improvements on a large scale (e.g., along an entire route or throughout a city). A guide on improving bus transit reliability would identify cost-effective techniques for improving bus reliability, thereby helping to improve ridership and provide more cost-efficient bus service.
The objective of this research is to develop a guide to bus transit service reliability. The guide will include a toolbox of resources that may be used to diagnose and manage bus transit service reliability and will describe benefits, costs, and outcomes of potential policies, strategies, and actions.
Accomplishment of the project objective will require at least the following tasks.
(1). Critically review and summarize North American and international literature on the causes of bus transit service unreliability; barriers to managing reliability; the impacts of unreliability on transit operations, costs, and ridership; methods of measuring reliability; service standards relating to reliability; and actions that transit agencies and roadway managers take to improve bus reliability. The review should include transit-system-related causes as well as external factors affecting reliability.(2). Identify and interview public transportation service providers who have undertaken steps to measure and improve reliability. Identify both successful and non-successful programs and identify factors that contribute to success or failure. This outreach should endeavor to obtain unpublished before-and-after studies and/or performance monitoring reports that document reliability improvement attempts and benefits and costs of the organization’s actions. A variety of bus-operating agencies should be contacted, ranging from large city urban systems to agencies providing low-frequency bus service in small cities and rural areas. Particularly effective and challenging programs could be included as case studies in the final guide. (3). Recommend performance measures from the passenger, agency, and operator perspectives for quantifying the effects of actions or treatments on bus reliability for inclusion in the Task 7 guide. Evaluate existing definitions of performance measures used to evaluate bus reliability (e.g., on-time performance, travel time variation, headway variation, excess wait time, punctuality, value of travel time). Issues to consider should include ease of data collection, typical applications, typical agency service standards, and compatibility with reliability measures used by other transportation modes (to allow apples-to-apples comparisons of reliability across modes). This task will evaluate how appropriate and effective these performance measures are in today’s information rich environment, leading to potential recommendations for new definitions and innovative performance measures. The Task 7 guide will include measures of provisions for adequate operator relief (e.g., bathroom breaks, meal breaks, turnaround time) and will identify agency procedures for implementing actions to improve bus service reliability.(4). Applying the results of Tasks 1 through 3, document the causes of bus service unreliability (both system-generated and externally caused); the relative magnitude of various causes; and potential operational, technological, and physical measures that might be used to improve reliability. Develop a prioritized list of measures to test based on the documented or likely magnitudes of their impacts on reliability or perceived reliability, cost, ease of implementation, and similar factors. (5). Develop a detailed work plan for Phase II, including identifying transit agencies that might be used as partners in testing particular actions. Prepare an initial outline of the guide to be developed during Task 7. Compile the results of Tasks 1 through 4 in an interim report.
(6). Conduct the approved Phase II work plan, which is anticipated to include a series of before-and-after evaluations of selected reliability-improvement techniques. This effort may include field studies, as appropriate for particular measures being evaluated; the availability of transit agencies willing to test particular measures; and the constraints of the project budget. Each evaluation should quantify the change in reliability (or customer perception of change) that occurred and describe the changes in before-and-after conditions. (7). Prepare a guide for transit agency staff across a variety of functions (e.g., planning, scheduling, operations, supervision, management) that describes the causes of unreliability at the stop, line, and system levels; recommends methods for measuring, diagnosing, and treating bus unreliability; describes the outcomes of reliability-improvement actions; and describes procedures for successfully implementing projects to improve bus reliability. Illustrative case studies should demonstrate how reliability is achieved from the passenger, operator, and agency perspectives. (8). Prepare a stand-alone technical memorandum titled “Implementation of Research Findings and Products.” (9). Final deliverables should include the following: (1) a guide to bus transit service reliability; (2) a final report summarizing the background research; (3) an updated interim meeting PowerPoint presentation suitable, upon revision, for posting on the project website; and (4) the Task 8 implementation technical memorandum.