Quantifying the Effects of Modal Conflicts on Transit Reliability
Residents of San Francisco, California, have repeatedly cited transit reliability as one of their top concerns. As San Francisco has begun investing in projects to reduce travel time variability, the trade-offs between alternatives have been difficult to quantify with existing tools. This study investigated and quantified the effects of modal conflicts on bus travel along a 3.6-mi study corridor and each conflict’s contribution to unreliability. Instances of modal conflict were modeled as Bernoulli trials or other simple probabilistic events and included vehicles entering or exiting parking spaces, double-parked vehicles, and vehicles queuing for pedestrians while executing turning movements. Cumulative distributions of modal conflict resulted in estimates of average delay and variance of delay from bus to bus. Sensitivity analyses illustrated and quantified the nonlinearity and variance of delay with respect to the number and severity of events. The convolution of distributions of delay for each conflict type could also be calculated, provided the causes of delay were independent. Modal conflict delay for a side-running bus rapid transit line in the study corridor was 1.9 min longer for buses with 95th percentile delays than for those with the mean delay of 4.2 min. Overall, the semi–standard deviation of delay compared with a no-modal-conflict reference point was 4.3 min. Furthermore, eliminating the analyzed modal conflict types along the study corridor—for instance, by establishing center-running bus-only lanes—could reduce system operating costs by up to $2.5 million per year and could result in user time savings equivalent to as much as $10.5 million per year.
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Availability:
- Find a library where document is available. Order URL: http://www.trb.org/Main/Blurbs/172232.aspx
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Authors:
- Wickland, Teo
- Sall, Elizabeth
- Publication Date: 2014
Language
- English
Media Info
- Media Type: Print
- Features: Figures; References; Tables;
- Pagination: pp 100–109
- Monograph Title: Transit 2014, Volume 4
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Serial:
- Transportation Research Record: Journal of the Transportation Research Board
- Issue Number: 2418
- Publisher: Transportation Research Board
- ISSN: 0361-1981
Subject/Index Terms
- TRT Terms: Bus lanes; Bus rapid transit; Bus transit; Delays; Reliability; Transportation corridors; Travel time
- Identifier Terms: Bernoulli's hypothesis
- Geographic Terms: San Francisco (California)
- Subject Areas: Planning and Forecasting; Public Transportation; I72: Traffic and Transport Planning;
Filing Info
- Accession Number: 01520026
- Record Type: Publication
- ISBN: 9780309295635
- Report/Paper Numbers: 14-5557
- Files: PRP, TRIS, TRB, ATRI
- Created Date: Mar 26 2014 10:13AM