S-134-V2-EN
Terminology
Piece cutting is the first stage of schedule optimization. Its goal is to determine all the potential vehicle pieces. This allows the optimization engine to rearrange duties in the most efficient way possible.
A vehicle piece is a sequence of vehicle events that is legal for a driver to do as a whole. A duty usually comprises multiple pieces.
Not every sequence of events is considered a valid piece. Here are some examples:
If a driver needs a break every 4 hours, a 5-hour sequence of events without a break is not a valid piece.
If a preference group has a rule where its drivers can only operate the routes from group A, any pieces from group B would be invalid for those drivers.
The vehicle piece validation tool lets you quickly determine whether a piece is valid or not. In this article, we go over the functionality and logic of the tool.
To find specific troubleshooting scenarios that involve the use of this tool, see this article.
Logic
Logically, a piece should start and end at a relief point or the depot, because it should be at a point in the route where the driver can get off the bus. This is why, depending on the optimization algorithm, pieces are cut at relief points (AFB algorithm) and/or during pull reliefs (DEEP algorithm).
The validity of a vehicle piece is defined by relief points, break preferences, and other factors we cover in this article. Invalid pieces are also called uncuttable because they cannot be cut during optimization.
The image below shows examples of valid and invalid pieces with Continuous breaks and Limit short pieces preferences set up:
There are also cases where a piece is valid, but there are no duties that can fully cover it. Example:
In the image below, Vehicle #1 performs 3 trips that are considered a valid piece. There are two duties in the pool: Duty A covers trips 567 and 5, Duty B covers trips 5 and
29, but there is no duty that could cover all three.
The piece validation tool is a feature in Scheduling that lets you quickly check if a vehicle piece is valid (cuttable).
How to use
To use the tool, follow these steps:
Highlight a piece in the vehicle Gantt by holding the SHIFT key and clicking on the first and last event in it.
A popup will appear, showing general info about the piece: its first and last stop, driving time, and so on. In the bottom-left of the popup, there is a piece validation tool button:
If you are using preference groups, before using the tool, select the correct group to validate the piece under. To do that, click the downward arrow button next to the cutting tool button and select the group in the list.
Click the piece validation tool button to validate the piece.
The result will be either Valid or Invalid. If Invalid, clicking the red arrow button will point to the reason why the piece does not work.
Note: If the piece starts or ends mid-trip, you will need to cut that trip. Click on the trip and press the 'U' key on the keyboard.
Relief opportunities layer
The Relief opportunities layer can help you visually identify relief points, which are crucial for valid vehicle pieces. To enable it, click the Layers button above the Gantt view and check the Relief opportunities box. All relief points will be marked by dotted vertical lines in the Gantt:
Note: whenever you update relief point preferences, Analyze the schedule so that the layer shows the updated points:
Piece cutting differences between AFB and DEEP algorithms
Piece cutting works slightly differently depending on the algorithm you use.
AFB (Advanced Fixed Blocks), the most commonly used algorithm, does not allow vehicle modification. As a result, piece cutting only happens at relief points and depots. With AFB, the piece validation tool will show why a piece cannot be cut.
DEEP allows for vehicles to be modified during duty optimization, so it can potentially add depot pulls to non-relief point terminal stops and use the resulting sequence as a piece. This will let you cut vehicle pieces that would not have been cuttable otherwise.
To learn how to enable DEEP, see this article.
Configuring pull reliefs with DEEP
When DEEP is enabled, follow these steps to configure pull reliefs and allow more flexibility in piece cutting:
Open Trip Connections.
Load the Pull reliefs template from the Optibus tab.
Select the stops that will serve as pull reliefs.
Save and close.
Note: The validation tool might still consider the piece invalid, but it will not cause errors during optimization.
Troubleshooting
To learn how to fix the most common piece-cutting errors, refer to this article.