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John Spence
 
 
John Spence - Mova specialist
 
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Modelling Mova

Mova responds to varying arrival flows to operate a signal controlled junction with minimum delay, and whenever possible will clear traffic from each approach every cycle until the junciton as a whole is saturated, above which priority is given to approaches according to user selectable criteria. Green durations and therefore cycle time vary according to demand within user pre-set constraints.

Modelling Mova

Traffic Signal capacity calculation programs, some of which are also useful for design purposes in particular for determining the optimum Method of Control, are empirical models in which input traffic flows and geometry are used to calculate delays, capacity and signal timings for a single optimum cycle running the average green times for a user-preset or optimised cycle time over the input traffic flow period. Within these constraints, these programs are highly reliable, well respected, and trustworthy, relying upon geometric parameters and traffic performance measurable on site, and offering results which can be calibrated and Validated against site performance. They have a robust and proven lineage in the profession. However, these traditional one shot empirical models can only be used to assess the optimum single average cycle in a traffic flow period. 

Mova Modelling

Assessment of how effective Mova can be in a specific scenario is with care capable of being assessed using microsimulation modeling techniques. These iterative models use behavioral characteristics to determine vehicle performance (although this is adjustable by the user on a lane by lane basis).

When combined with either TRL’s PCMova or the more flexible Controller Functionality models to read detector transitions from the model and send green durations to the model, this enables the use of model analytical and statistical techniques to assess how effective the system is over a number of signal cycles and iterations over a period, including testing the use of any mode (fixed time, CLF, VA or Mova) or traffic flow scenarios. 

Microsimulation techniques however, unless carefully set up, often do not model arrival pattern variations arising from upstream junctions, nor often of arrival rate variations within the peak hour, hence may not reflect peak arrival rates which occur at peak of peak.

PCMova is adequate for simple applications; for more complex and Linked Mova Schemes the emerging Controller Functionality models are essential, and are proving to be reliable indicators of operational performance, capable of model pre-site Validation.

Both techniques are becoming reliable tools (subject only to microsimulation models providing more realistic simulation of arrival rate fluctuations), although without yet a proven track record of before and after measurements prior to implementation to calibrate the model and after implementation taking measurements of performance and queuing to confirm the model achieved reliable results.

junction modelling
 
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