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Passenger car units in saturation flows: Concept, definition, derivation

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  • Kimber, R. M.
  • McDonald, M.
  • Hounsell, N.

Abstract

Passenger car units (pcus) are traditionally used to represent the effects of changes in traffic composition (the mix of cars, goods vehicles, buses, ad so on) on the saturation flows at traffic signal junctions. This paper describes in the results obtained by the two main methods of derivation of pcu values, regression analysis of asynchronous vehicles counts (asynchronous regression) and headway ratio methods, when applied to data from two large public road studies. The relationship between the various methods of derivation used is investigated. Regression analysis of synchronous vehicle counts, Webster's method, and headway ratio methods are seen to agree, but asynchronous regression necessarily gives lower results so long as there is variability in the headways of vehicles of a given class (e.g. in car-to-car headways). Alternative method of regression analysis of asynchronous counts is investigated but found to be biased, although les so than the existing method. Conventional asynchronous regression gives unbiased saturation flow estimates if unbiased prior pcu values are used. The effects of assumed pcu values on signal settings and consequent delays in subsaturation conditions are examined. Value corresponding to delay-minimising settings are close to the ratio of the mean headways of the appropriate vehicle classes.

Suggested Citation

  • Kimber, R. M. & McDonald, M. & Hounsell, N., 1985. "Passenger car units in saturation flows: Concept, definition, derivation," Transportation Research Part B: Methodological, Elsevier, vol. 19(1), pages 39-61, February.
    • Handle: RePEc:eee:transb:v:19:y:1985:i:1:p:39-61
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    Cited by:

    1. Li, Tongfei & Cao, Yaning & Xu, Min & Sun, Huijun, 2023. "Optimal intersection design and signal setting in a transportation network with mixed HVs and CAVs," Transportation Research Part E: Logistics and Transportation Review, Elsevier, vol. 175(C).
    2. Yeung, Jian Sheng & Wong, Yiik Diew & Secadiningrat, Julius Raditya, 2015. "Lane-harmonised passenger car equivalents for heterogeneous expressway traffic," Transportation Research Part A: Policy and Practice, Elsevier, vol. 78(C), pages 361-370.
    3. Yi Wang & Jian Rong & Chenjing Zhou & Xin Chang & Siyang Liu, 2020. "An Analysis of the Interactions between Adjustment Factors of Saturation Flow Rates at Signalized Intersections," Sustainability, MDPI, vol. 12(2), pages 1-18, January.
    4. Hossain, M., 2001. "Estimation of saturation flow at signalised intersections of developing cities: a micro-simulation modelling approach," Transportation Research Part A: Policy and Practice, Elsevier, vol. 35(2), pages 123-141, February.
    5. Fernandez, Rodrigo & Valenzuela, Eduardo & Casanello, Federico & Jorquera, Carola, 2006. "Evolution of the TRANSYT model in a developing country," Transportation Research Part A: Policy and Practice, Elsevier, vol. 40(5), pages 386-398, June.
    6. Li, Hongwei & Zhong, Xin & Zhang, Wenbo & Li, Sulan & Xing, Yingying, 2020. "An algorithm for e-bike equivalents at signalized intersections based on traffic conflict events number," Transportation Research Part A: Policy and Practice, Elsevier, vol. 134(C), pages 78-95.
    7. Wei Xu & Dillip Kumar Das & Željko Stević & Marko Subotić & Adel F. Alrasheedi & Shiru Sun, 2023. "Trapezoidal Interval Type-2 Fuzzy PIPRECIA-MARCOS Model for Management Efficiency of Traffic Flow on Observed Road Sections," Mathematics, MDPI, vol. 11(12), pages 1-22, June.
    8. Benekohal, Rahim F. & Zhao, Weixiong, 2000. "Delay-based passenger car equivalents for trucks at signalized intersections," Transportation Research Part A: Policy and Practice, Elsevier, vol. 34(6), pages 437-457, August.
    9. Saha, Arpita & Chakraborty, Souvik & Chandra, Satish & Ghosh, Indrajit, 2018. "Kriging based saturation flow models for traffic conditions in Indian cities," Transportation Research Part A: Policy and Practice, Elsevier, vol. 118(C), pages 38-51.

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