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Suggested Citation:"Overview and Summary." National Academies of Sciences, Engineering, and Medicine. 2004. Traveler Response to Transportation System Changes Handbook, Third Edition: Chapter 9, Transit Scheduling and Frequency. Washington, DC: The National Academies Press. doi: 10.17226/23433.
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Page 1
Page 2
Suggested Citation:"Overview and Summary." National Academies of Sciences, Engineering, and Medicine. 2004. Traveler Response to Transportation System Changes Handbook, Third Edition: Chapter 9, Transit Scheduling and Frequency. Washington, DC: The National Academies Press. doi: 10.17226/23433.
×
Page 2
Page 3
Suggested Citation:"Overview and Summary." National Academies of Sciences, Engineering, and Medicine. 2004. Traveler Response to Transportation System Changes Handbook, Third Edition: Chapter 9, Transit Scheduling and Frequency. Washington, DC: The National Academies Press. doi: 10.17226/23433.
×
Page 3
Page 4
Suggested Citation:"Overview and Summary." National Academies of Sciences, Engineering, and Medicine. 2004. Traveler Response to Transportation System Changes Handbook, Third Edition: Chapter 9, Transit Scheduling and Frequency. Washington, DC: The National Academies Press. doi: 10.17226/23433.
×
Page 4

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

9-1 9 – Transit Scheduling and Frequency OVERVIEW AND SUMMARY Information on traveler response and related impacts is presented in this “Transit Scheduling and Frequency” chapter for scheduling changes made to conventional bus and rail transit, including changes in the frequency of service, hours of service, structuring of schedules and schedule reliability. Frequency changes made together with fare changes are included. This chapter does not, however, cover transit routing and coverage changes. They are covered in other chapters as detailed at the end of this introduction. Within this “Overview and Summary” section: • “Objectives of Scheduling and Frequency Changes” outlines reasons for such actions. • “Types of Scheduling and Frequency Changes” lists and defines the scheduling changes and combinations addressed in this chapter. • “Analytical Considerations” covers methods used in quantifying response to schedule changes, limitations of available research, and cautions that thus apply to its use. • “Traveler Response Summary” highlights the travel demand findings for scheduling and frequency changes. The recommended approach to using either the “Traveler Response Summary,” or the material which follows, is to do so only after first reading the initial three subsections of this “Overview and Summary” for background. Following the four-part “Overview and Summary,” greater depth and detail are provided: • “Response by Type of Strategy” describes the travel demand effects of scheduling changes in terms of service or headway elasticities, ridership, and other measures. • “Underlying Traveler Response Factors” examines the role of the different components of travel time as well as considerations such as physical, operating and economic conditions. • “Related Information and Impacts” presents subtopics such as mode versus route choice effects, peak versus off-peak response, and environmental and cost considerations. • “Case Studies” expands on one multi-faceted demonstration project and three other instances of extensively analyzed frequency changes. The subject matter of this chapter, scheduling and frequency, covers a relatively specialized aspect of public transit operations. Chapter 10, “Bus Routing and Coverage,” broadens the coverage of conventional bus operations, as does Chapter 4 for express bus services, and Chapters 7 and 8 for urban rail systems. All aspects of demand responsive and ADA (Americans

9-2 with Disabilities Act) services are covered in Chapter 6, even matters of “scheduling” (dispatching) and service quantity. Objectives of Scheduling and Frequency Changes Scheduling and frequency modifications are among the most common service changes that transit operators make to improve service effectiveness. Both cost effectiveness and service quality are primary goals to be served, with appropriate trade-offs. A cost effectiveness operating objective where transit use is high is to adjust capacity to demand, for adherence with passenger loading standards and productive distribution of service. A related objective applicable in all circumstances is to increase transit vehicle and crew utilization efficiency. The overriding service quality objectives of scheduling and frequency changes are to minimize overall passenger trip time and enhance convenience. The resulting traveler response is of concern whichever the perspective — cost savings or service enhancement. A better understanding of the response of riders to frequency changes should result in design of more effective service modifications (Miller and Crowley, 1989). Scheduling and frequency most particularly affect that aspect of transit service quality which is the waiting time patrons encounter and perceive in making a transit trip. Individual changes may have the objective of reducing wait time at the start of a transit trip, or minimizing wait time if a transfer between two vehicles is required. Scheduling changes may be made to increase the ease of passenger comprehension of the schedule. Related actions may have the objectives of improving the reliability of the service, reducing both real and perceived passenger wait times, and lowering passenger anxiety. These service quality objectives support the goals of providing a more attractive service, increasing transit ridership, and shifting travel out of low occupancy autos. Types of Scheduling and Frequency Changes Scheduling and frequency changes generally involve the manipulation of service hours and headways, and details of transit vehicle arrival and departure timing. Such changes are, in effect, a specialized form of transit service improvement or reduction that involves no alteration of coverage or routing. The following general types of changes are discussed further within this chapter: Frequency Changes. This strategy involves increasing or reducing the number of scheduled transit vehicle trips to provide an increase or decrease in service frequency. Headways and passenger wait times are correspondingly shortened or lengthened.1 Such changes may be concentrated in the peak or off-peak periods, or may apply overall. Service Hours Changes. Under this strategy the span of service is increased or decreased by lengthening or shortening the service day during which service is provided, or by adding or eliminating days of service, such as Sunday operation. The hours during which taking transit is 1 Service frequency is the number of buses or trains per hour or day, while the headway is the time interval between buses or trains. Passengers arriving randomly will, if the transit service is reliable, have a waiting time which averages one half the headway.

9-3 an option are correspondingly increased or constrained, and the likelihood of being stranded without service is likewise affected. Frequency Changes with Fare Changes. Frequency changes (and service hours changes) are often implemented in conjunction with fare changes. Pairing frequency reductions with fare increases is a common approach to transit deficit reduction, while increased frequency may be implemented together with decreased fares to up ridership and enhance value received by the consumer. Combined Service Frequencies. This approach is the outcome of offering a combination of different transit services to address diverse needs of patrons, while concurrently providing service frequency options to selected markets. For example, overlaying express service onto local service on the same street provides service tailored to passengers making both long and short trips. At the same time, for trips that can be made by boarding and alighting where both service types stop, this approach provides the option of either taking the next bus or waiting for the preferred service. Regularized Schedules. This strategy uses rescheduling to obtain regularized service frequency and associated benefits. Regularized schedules can result in easy-to-remember departure times, matches with regularly scheduled activities, or better coordination at transfer points. Timed transfers minimize transfer wait times and, therefore, reduce total travel times for multi-route passengers. Rescheduling and frequency adjustments are often included as elements of more extensive transit service modifications. Such combinations are, in the main, discussed in Chapter 10, “Bus Routing and Coverage.” Analytical Considerations Changes in both individual transit route headways and more broadly based service levels, major aspects of scheduling and frequency, lend themselves to impact quantification using elasticities to describe the response of transit ridership. Elasticities are convenient and useful in this regard, but whether case-specific or generalized, require caution in their interpretation and application (see also Chapter 1, “Introduction,” under “Use of the Handbook” — “Concept of Elasticity”). Results of service frequency changes are often not fully distinguishable from the effects of other concurrent service alterations, such that empirically derived elasticities and like measures frequently reflect the influence of other actions. Similar to the situation in other transit service change topics, much of the more detailed information on scheduling and frequency change effects is old. Available recent findings, however, do suggest that basic relationships between transit service level changes and impacts on ridership are remaining stable over time. Although there are long term social and economic trends that have altered the usage of public transit, interpretation of older data on response to scheduling and frequency changes is not complicated by shifts in travel patterns in the way that raises special concern for evaluation of strategies with a strong spatial component, such as routing changes or system reorientation. Reliability Changes. Reliability of service is an issue allied with scheduling. Lack of reliability can take the form of deviations from scheduled arrival and departure times, transit vehicle or train trips missed altogether, or both. Correction reduces passenger wait time, delay and uncertainty.

9-4 The “unlinked trip” system of reporting transit usage, which counts each boarding whether at the start of a trip or at a transfer point, does not cause problems for interpretation of most scheduling and frequency changes. It does, however, severely complicate evaluation of those timed transfer strategies which involve introduction of routes which terminate at the timed transfer “pulse point,” as compared to use of through routing at the “pulse point.” Any action which forces transfers increases the unlinked trip count without necessarily increasing the number of transit passengers. Only with linked trip survey data or transfer rate information can such service changes be satisfactorily evaluated. The environment within which a transit service change takes place will affect the results, and this places a special burden on the analyst seeking to judge the transferability of traveler response findings from one situation to another. The handful of cases where local economic conditions have been reported tend to suggest that response to frequency improvements in particular may be significantly affected by the state of the local economy. This and other possible effects of the operating environment are discussed further in the “Underlying Traveler Response Factors” section. Additional guidance on using the generalizations and examples provided in this Handbook is offered in the “Use of the Handbook” section of Chapter 1. Please note that throughout the Handbook, because of rounding, figures may not sum exactly to totals provided, and percentages may not add to exactly 100. Traveler Response Summary The traveler response to service frequency changes varies substantially. Ridership increases proportionately exceeding the frequency increases they are related to have been observed, reflecting an elasticity in excess of +1.0, but not often. Circumstances where frequency improvements failed to attract new ridership at all are also reported. The average response to frequency changes, including both increases and decreases, approximates an elasticity of +0.5 as measured in terms of response to service quantity.2 Extremely limited information suggests that the hours service is offered can be as important as frequency. There are underlying patterns that relate to at least some of the widely varying circumstances and results attending individual transit service modifications. Ridership is typically most sensitive to frequency changes when the prior service was infrequent, such as hourly or half-hourly, and when the transit line involved serves middle and upper income areas. Where transit headways are already short, and particularly when lower income service areas are involved, ridership tends to be less affected by frequency changes and may be more sensitive to fare changes. Otherwise, ridership is typically more responsive to frequency changes than fares. There is normally a higher sensitivity to frequency changes on the part of off-peak riders than there is by peak period ridership. 2 A service elasticity of +0.5 indicates a 0.5 percent increase (decrease) in ridership in response to each 1 percent service increase (decrease), calculated in infinitesimally small increments. An elastic value is +1.0 or greater and indicates a demand response which is more than proportionate to the change in the impetus. Elasticities reported in this chapter are thought to all be either mid-point arc or log arc elasticities, which are very similar, and if not are almost certainly from other closely equivalent computations (see “Use of Handbook” — “Concept of Elasticity” in Chapter 1, “Introduction,” and Appendix A, “Elasticity Discussion and Formulae”).

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TRB’s Transit Cooperative Research Program (TCRP) Report 95: Chapter 9 – Transit Scheduling and Frequency examines scheduling changes made to conventional bus and rail transit, including changes in the frequency of service, hours of service, structuring of schedules, and schedule reliability.

The Traveler Response to Transportation System Changes Handbook consists of these Chapter 1 introductory materials and 15 stand-alone published topic area chapters. Each topic area chapter provides traveler response findings including supportive information and interpretation, and also includes case studies and a bibliography consisting of the references utilized as sources.

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