The Centre for Transport Studies is pleased to welcome
Mr Nicholas Taylor (Centre for Transport Studies, UCL)
to lead a seminar entitled
Green period capacity and stochastic signal queues
to be held
Wednesday 08 May 2013 @ 16:00
Please join us for presentation and discussion at
Room 208, Chadwick Building, UCL
Maps and travel directions: http<http://www.cege.ucl.ac.uk/people/Pages/How-to-find-us.aspx>://<http://www.cege.ucl.ac.uk/people/Pages/How-to-find-us.aspx>www.cege.ucl.ac.uk/people/Pages/How-to-find-us.aspx<http://www.cege.ucl.ac.uk/people/Pages/How-to-find-us.aspx>
Abstract
Analytical models of signal queues, such as Webster and Cobbe’s formula and the HCM delay function, include the mean stochastic queue resulting from random and oversaturation effects. This is idealised as an M/D/1 process with random arrivals and uniform service. It has been noted that this queue depends on absolute green period capacity, as well as green/cycle ratio etc. This can be accommodated by a modified formulation which unlike basic M/D/1 appears not to offer closed-form moments usable in macroscopic traffic models. Some existing approximations are accurate only for demand near capacity. We present an alternative approach based on a linkage between traffic intensity and green period capacity verified by Markov simulations which estimates both equilibrium mean and variance with fair accuracy, giving enough information for estimating equilibrium probability distributions. A general method for estimating distributions based on doubly-nested Geometric distributions is also described.
About the Speaker
Nicholas Taylor has worked for many years at TRL, and was responsible for later versions of the CONTRAM traffic assignment software. While continuing as project manager or technical lead at TRL, he has been pursuing PhD research at UCL to extend methods in time-dependent queuing theory, with the aim of calculating variability along with mean queue profiles, and widening the range of queue processes that can be modelled in this way. The presentation will describe some of the latter work.
Next CTS Seminar
Ms Sabine Wilke (Centre for Transport Studies, Imperial College) will be leading a seminar titled “A framework for assessing the quality of aviation safety databases” at Imperial College on Wednesday 15th May @ 16:00
About the CTS Seminar Series
The CTS seminar series aims to facilitate discussion on current research topics in the transport field. Seminars are held jointly with our colleagues in the Centre for Transport Studies at University College London. They are usually held on Wednesday afternoons at Imperial College London or University College London.
Seminars are free of charge and open to all interested parties. Booking is not required.
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CTS home: www.imperial.ac.uk/cts<http://www.imperial.ac.uk/cts> (Imperial College London)
www.cege.ucl.ac.uk/cts<http://www.cege.ucl.ac.uk/cts> (University College London)
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