One of the most important features of SIDRA INTERSECTION is the modelling of signal platoons for signal coordination effects in network analysis. This is a unique lane-based platoon model derived using second-by-second arrival and departure flow patterns as a function of signal Offsets.
Unlike traditional network models that use aggregate models of links or lane groups, SIDRA INTERSECTION uses a lane-based model for platoon movements between upstream and downstream Sites (on internal approaches). This provides information about upstream departure and downstream arrival patterns, queue lengths, lane blockage probabilities, proportion of traffic arriving during green, and so on at an individual lane level.
The model applies to the internal approaches of two or more Coordinated Signal Sites that are connected to each other. The model also applies to two Coordinated Signal Sites with continuous lanes at a Site between them, for example Major Road lanes (treated as continuous lanes) of Two-Way Sign Control Sites, or continuous lanes at a seagull T intersection, between two Coordinated Signal Sites. The platoon patterns are moved from the upstream Site to downstream Site through the continuous lanes in this case.
The model takes into account midblock lane changes that apply to signal platoon patterns. This is particularly important in evaluating closely-spaced (paired) intersections with high demand flows where vehicles have limited opportunities for lane changes between intersections.
In addition to the new Platoon Model using Signal Offsets, the traditional Simple Platoon Model using Arrival Types or Percent Arriving During Green continues to be available, and can be useful for example for external approaches of a Network.
Refer to the User Guide for detailed information on this subject. Also see the new papers on our Articles page.
For the new second-by-second lane-based platoon model to apply to connected Signal Sites in a Network, you must ensure that the relevant input parameters are set correctly:
- Set the Signal Coordination parameter as Program in the Signals tab in the Vehicle Movement Data dialog for each Site. In your existing Projects, these may have been specified as Arrival Type or Percent Arriving during Green. Change these to the Program option if you want the new second-by-second lane-based platoon model to apply.
- Set the Reference Phase in the Phase & Sequence data tab of the Phasing & Timing dialog for each Site.
- Specify the signal coordination data (Coordinated Site, Reference Site, Offset, Network Cycle Time, Site Phase Times) in the Network Timing dialog.
- Check the parameter Apply Platoon Dispersion in the Network Data dialog if you wish to include modelling of platoon dispersion.
The COORDINATION INFORMATION table in the Coordination and Actuated Signal Information group of the Detailed Output report includes the Platoon Ratio, Percent Arriving During Green and Arrival Type determined by the second-by-second platoon model for individual internal approach movements.
The Platoon Ratio and other signal coordination parameters given in the COORDINATION INFORMATION table of the Detailed Output report for movements are indicative of progression quality but they are not used directly in the performance models. Instead, the SIDRA INTERSECTION model uses signal coordination parameters determined for internal approach lanes. These are given in the COORDINATION PARAMETERS table in the Lane Performance and Capacity Information group of the Detailed Output report.
Using the Platoon Ratio parameter for each lane, SIDRA INTERSECTION calculates Delay Progression Factor and Queue Progression Factor parameters for use in performance calculations. These parameters are included in the COORDINATION PARAMETERS table as well as the LANE DELAYS and LANE QUEUES tables in the Detailed Output report.