S-093-V1-EN
Sometimes crew optimization may take longer than expected. If this is the case, it is likely because the platform has a vast amount of potential solutions to consider, which can increase computation time.
There are two parameters that typically affect crew optimization speed – the limit short pieces template, part of the custom duty preference, and the retention ratio, part of the algorithm parameters preference. We recommend adjusting these two parameters to find the right balance between faster optimization on the one hand and more scheduling options on the other.
Limit short pieces
The limit short pieces template is part of the custom duty preference and indicates the shortest amount of driving time (or "piece") that can be associated with a vehicle on the schedule for any given trip.
1. In Scheduling, go to schedule preferences by clicking the Preferences tab in the top left of the screen.
2. Select the custom duty preference by typing it in the search bar or looking in the Drivers category. (If this preference is not in use, first click ALL to see all preferences.)
3. Click Load Template at the bottom of the pop-up screen.
4. Click the OPTIBUS tab and select the 'Limit Short Pieces' template. Click Apply.
5. Define your preferences to limit short pieces:
Minimum piece length: The shortest amount of driving time (in minutes) that can be associated with a vehicle on the schedule for any given trip
Minimum joined piece length: The shortest amount of driving time (in minutes) that can be associated with a vehicle on the schedule when joined with another "piece" of driving time for the same trip
We recommend selecting a duration of 60, 90, or 120 minutes.
You may have to try different piece lengths to determine the right balance between having more scheduling options (you will have more options when the pieces are shorter) and having faster optimization (you will have fewer options and faster optimization when the pieces are longer).
If you have many short trips, a shorter duration might work better. If your trips tend to be longer, a longer duration might work better.
If a minimum piece length is not set, vehicles may be allocated any amount of driving time.
6. After defining the "Limit short pieces" template, it's important to make sure the constraint imposed on short pieces can be relaxed in cases where the constraint makes it too difficult to create a viable schedule. To do this:
Search for the crew relaxation preference (in the Drivers category), and click the Add Preference button.
Click the checkbox next to "Limit short pieces."
Retention ratio
The retention ratio under the algorithm parameters preference is a parameter that refers to the percentage of three-piece duty (duties that include two vehicle changeovers) candidates that will be considered. Note that you can use this parameter only if you allow more than 1 changeover per duty (since 3 piece duty includes two vehicle changeovers).
This number should be set to any value higher than zero and lower than or equal to 1. A value of 1 indicates that we consider all possible three-piece duty candidates, while a value of 0.5 indicates we consider only 50% of such duties. Therefore, if we want to reduce the running time we can reduce this value.
To change the retention rate:
Go to the preference, and search for algorithm parameters
Reduce the retention ratio value and save.