SPEED AND DELAY PREDICTION MODELS FOR PLANNING APPLICATIONS

Estimation of vehicle speed and delay is fundamental to many forms of transportation planning analyses including air quality, long-range travel forecasting, major investment studies, and congestion management systems. However, existing planning-level techniques do a poor job of estimating the duration and extent of congestion. To improve the state of the practice, a simplified queuing-based model, QSIM, was developed. QSIM incorporates several features including: the use of temporal distributions as a basis for developing hourly traffic estimates; estimation of "peak spreading"; accounting for daily variation in traffic by allowing hourly traffic estimates to vary stochastically; for freeways, the inclusion of a capacity drop after flow has broken down (i.e., after the onset of queuing) to model the growth and dissipation of queues; for arterials, considering the effects of signal density and progression; separate functions to estimate speeds in queuing and free-flow conditions, based on relationships developed with microscopic traffic simulation models; use of the concept of highway capacity to determine when traffic operates under free-flow and queuing conditions, as well as a basis for estimating free-flow speeds and the extent of queuing in the test link; and estimating delay rather than speed as the predictive variable. (Speed is then developed as a function of delay and free-flow speed). The model was used to develop a dataset from which a series of predictive equations were developed. The equations use only a few, readily available independent variables. Application of the new procedure shows that under congested conditions, it predicts substantially more delay than do traditional methods. Future work includes field validation of the models and extending them to cover a variety of bottleneck conditions.

• Record URL:
  https://doi.org/10.21949/1403576
• 
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/12936
• Supplemental Notes:
  • Conference proceedings available only on CD-ROM.
• Corporate Authors:

  Washington State Department of Transportation

  Transportation Building, 310 Maple Park Avenue SE, P.O. Box 47300
  Olympia, WA  United States  98504-7300
• Authors:
  • Margiotta, R
  • Cohen, H
  • DeCorla-Souza, P
• Conference:
  • Sixth National Conference on Transportation Planning for Small and Medium-Sized Communities
  • Location: Spokane Washington, United States
  • Date: 1998-9-16 to 1998-9-18
• Publication Date: 1999

Language

• English

Media Info

• Pagination: 32p
• Monograph Title: SIXTH NATIONAL CONFERENCE ON TRANSPORTATION PLANNING FOR SMALL AND MEDIUM SIZED COMMUNITIES, SEPTEMBER 16-18, 1998, SPOKANE, WASHINGTON

Subject/Index Terms

• TRT Terms: Equations; Free flow speeds; Mathematical prediction; Queuing theory; Speed and delay studies; Stochastic processes; Traffic congestion; Traffic estimation; Traffic flow; Transportation planning
• Subject Areas: Data and Information Technology; Highways; Planning and Forecasting; I72: Traffic and Transport Planning;

Filing Info

• Accession Number: 00780089
• Record Type: Publication
• Files: NTL, TRIS, STATEDOT
• Created Date: Dec 6 1999 12:00AM