Applying weighting factors is a great way to customize the optimization routine in Synchro 9. If you haven't tried this new feature yet, this post will get you started. Weighting factors allow you to favor specific movement(s) at some or all of the intersections in the network. There are two choices to apply weighting factors, to specific phase(s) or there is a shortcut to apply a single weighting factor to all of the coordinated phases. Choose which method to use in the Optimize Cycle Lengths window.
Here is a sample arterial that has been optimized using no weighting factors.
A Cycle Length of 130s was selected. Using these default optimization settings, the total delay for the entire network is 234 hours, with an average speed of 15mph. In the time-space diagram below, you can see a EB bandwidth of 15s and a WB band of 40s.
These are pretty good results, but now let's add some weighting factors and see if we can improve the progression. This time we assigned a weighting factor of 4.0 to all of the Reference Phases.
The same Cycle Length was selected, but the weighting factor will modify the splits to favor the reference phases. The total delay has increased to 225 hours for the entire network but the average speed has increased to 16mph. The longer cycle length has increased the delay for side-streets and left-turns. However, the travel time on the major street have been improved. In the time-space diagram below, you can see a EB bandwidth of 22s and a WB band of 43s.
As for which of these timing plans is "better", it depends on the goals of the project: overall delay or major street travel times?
You can also assign a specific weighting factor to phases at any intersection(s) in the Phasing Settings window. This is a great way to deal with something like a problematic left-turn or side-street that isn't a coordinated phase. It also gives you the flexibility to assign different weighting factors at each intersection.
We hope you enjoy the increased flexibility that weighting factors provide! There are many strategies to designing a timing plan, and we'd love to hear how these are working for you.