A couple of difficulties exist in analysing signalised paired intersection systems. These are related to:
- use of a common (single) signal controller to control the paired intersection system, and
- the need for Dummy Movements in phase sequence specifications.
These are explained below.
Common Signal Controller
If the component Sites of a paired intersection system operate under a common signal controller, the same phase sequences must be specified and same Phase Times given for the component Sites. In this case, common Phase Times should be given in the Phase & Sequence Data tab of the Phasing & Timing dialog, and the User-Specified option should be selected for Site Phase Times in the Network Timing dialog.
When the Program option is selected for Site Phase Times in the Network Timing dialog, the timing analysis for each Site will be carried out separately resulting in different Phase Times for component Sites. Common Phase Times can be determined by comparing required times for critical movements for component Sites and choosing the highest value for each phase at any Site using the Critical Movements and Cycle Time table given in the Signal Timing section of the Detailed Output report for each Site. An example is given in the User Guide.
In phase sequences specified for component Sites of a paired intersection system, it may be necessary to add Dummy Movements in one or more phases for each Site when the timing analysis for the component Sites are done separately if this results in one of the messages " there is no movement starting in phase …" or "there is no movement ending in phase …".
Dummy Movements are introduced in the Phase & Sequence Data tab of the Phasing & Timing dialog. These movements do not exist physically, volume data cannot be given and no capacity or performance estimation is carried out for them. They are used are for the purpose of signal timing calculations only. For further information on Dummy Movements, refer to the User Guide.