The probability of delay to minor stream drivers at a limited priority freeway merge

Bunker, Jonathan M. & Troutbeck, Rodney J. (1996) The probability of delay to minor stream drivers at a limited priority freeway merge. Road and Transport Research: a journal of Australian and New Zealand research and practice, 5(1), pp. 16-25.


Gap acceptance theory is traditionally based on the interactions when a minor stream of drivers wish to enter a major stream generally assumed to have absolute priority. However, some researchers have felt that this model is not always appropriate. In analysing freeway merging behaviour, it was found that major stream drivers have only limited priority, suffering some delay. This report discusses the development of a relationship to predict the probability of merging drivers being delayed at a limited priority freeway merge after leaving an unsignalised intersection upstream. This quantity is a valuable performance measure itself, and with average merging delays able to be predicted, facilitates tangible merge area performance assessment. Equations formulated to represent probability of delay against degree of saturation are compared. A new relationship is proposed, which indicates that critical gap has only a marginal influence on probability of merging delay, and that flow rates in both minor and major stream have a significant and adverse influence. It is suggested that the maximum acceptable (or practical) probability of merging delay should be approximately 60%. This gives results which are similar to maximum measured downstream kerb lane flows.

Impact and interest:

7 citations in Scopus
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ID Code: 10679
Item Type: Journal Article
Refereed: Yes
Additional URLs:
Keywords: gap acceptance, traffic modelling, limited priority, freeway, traffic delay, merge area, critical gap
ISSN: 1037-5783
Subjects: Australian and New Zealand Standard Research Classification > ENGINEERING (090000) > CIVIL ENGINEERING (090500) > Transport Engineering (090507)
Divisions: Past > QUT Faculties & Divisions > Faculty of Built Environment and Engineering
Copyright Owner: Copyright 1996 Australian Road Research Board
Copyright Statement: Reproduced in accordance with the copyright policy of the publisher
Deposited On: 12 Nov 2007 00:00
Last Modified: 09 Jun 2010 12:48

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