Bus priority and queue relocation using pre-signals

Sirivadidurage, Sansaka Pradeep Kumara (2006) Bus priority and queue relocation using pre-signals. University of Southampton, Doctoral Thesis.

Abstract

This thesis evaluates a congestion management strategy called pre-signals, which offers uses priority access to a downstream junction using appropriate combinations of physical segregation, and advanced traffic signal control techniques. The two main control techniques used are known as bus priority and queue relocation.  There is limited literature that describes the design and evaluation techniques for pre-signals.  Therefore production of compatible design and evaluation techniques for the scheme filtration and selection of suitable sites as possible from results of this research is considered to provide an important contribution to the practice.

The research described in this thesis developed analytical modelling and controlled microscopic simulation combined with field data to obtain a comprehensive evaluation of pre-signal systems.  The proposed analytical technique modified ‘control delay’ methods from the US Highway Capacity Manual to evaluate pre-signals.  The relationships introduced to cater for possible interactions bridge a gap in literature especially in designing and evaluation pre-signals.  Microscopic traffic simulation was proposed to evaluate more complex situations as it was capable of modelling complicated and site specific traffic operations which are common at pre-signals.  Simulation-based analyses are often conducted under default parameter values or ‘best guessed’ values due to the difficulty in field data collection of lack of readily available procedures on model calibration.  A calibration procedure was therefore developed which was shown to systematically improve the prediction accuracy from simulation.  The research also produced proposed guidelines for design and evaluation of pre-signals, which would be an important contribution to practice.

Results indicated that in the right circumstances a pre-signal is capable of providing a strong priority to buses at congested road sections via bus priority and queue relocation techniques.  Appropriate design and control can minimise any additional delay to other traffic. The effectiveness of a pre-signal and control can minimise any additional delay to other traffic.  The effectiveness of a pre-signal should be judged not by vehicle throughput but by passenger throughput.  In this sense a pre-signal may be an effective device to offer buses a strong priority.

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