TPAC Pairing

TPAC^TM Pairing is part of the TPAC^TM suite of crew planning tools. It automatically creates a set of optimized crew pairings for schedules that are too large for manual pairing creation. It ensures that the crew pairings have a minimized cost subject to the constraints given by the crew work rules and the desire for a solution that is robust to disruptions.

What is Crew Pairing?

Crew pairing is the process of pairing crews with legs of a vehicle schedule such that:

• All legs in the schedule are crewed.
• The crew start and end each pairing at their base.
• All legislative and industrial work rules are obeyed for each pairing.

Crew Pairing deals with "virtual" crews; no identifying data is included in the process, just the numbers and skills required. Pairing Optimization is generally, but not exclusively, applied to aircraft and train crews. The objective is to reduce the total manpower to service any given schedule and fleet assignment.

What are the Challenges in Crew Pairing?

Crewing of a transport schedule would be a simple problem if crew could work non-stop like vehicles - it would simply be a matter of the crew staying with the vehicle all day. Vehicles like aircraft and trains are expensive assets whose utilization must be maximized, so they cannot stand idle while their crews take a break. For such equipment it is necessary for crew to be matched with different vehicles over the course of a duty period.

Furthermore, when it is not practical for a vehicle to return to a central point whenever there is a crew change, it is necessary to produce crew pairings that change vehicles at intermediate ports or stations. The resulting pairing creation process thus becomes much more complicated than a simple rostering problem, as it is necessary to have a crew waiting at these points ready to take over from the crew whose duty is finishing.

For long haul schedules, a pairing might also incorporate one or more "layovers" - that is one or more nights of rest in a hotel between duties. Pairings may also include transfers via other modes of transport or legs operated by different operators, and may also include duties such as training, shunting, standby duty etc.

A good set of crew pairings has the following characteristics:

• Every leg of a schedule is paired with only one crew, i.e. within a pairing there should be few or no "paxing" or "deadheading" legs where the crew is traveling in order to be in position for operating another leg. Such legs are unproductive, and may also incur an additional cost.
• Each crew works for close to their maximum permitted work time each day, thus minimizing the number of crew required to crew the schedule when rostering is performed.
• There are as few vehicle changes as possible, as these mean that disruptions to one vehicle can cause disruptions to other vehicles. This increases the robustness of the crew pairing solution.
• Vehicle changes have some slack time built in to minimize the flow on effect of disruptions, but not too much, for then the crew would be paid to wait around.
• All legislative and company rules regarding maximum work times, required meal breaks etc. are obeyed.

How is TPAC Pairing used?

TPAC^TM Pairing has been designed to handle all pairing requirements for a transport enterprise including:

• Planning: The overall planning process starts with downloading the schedules from the scheduling system's database. The number and categories of crew required for each leg can be specified in the downloaded schedule, or specified separately according to equipment type and configuration.
• Just in Time Crew Assignment: Just in time crew assignment is a way of coping with a situation where significant changes to schedules often occur after work days have been assigned to crew members. The crew members are assigned blocks of working days according to the planned pairings, but the actual legs operated by each crew member are only finalized a few days in advance of the start of the block. This process is repeated each day.
• Repair of Disrupted Pairings: On the day of operations, planned pairings may be disrupted by delays and cancellations. TPAC^TM Pairing automatically detects which pairings are now illegal, and modifies existing pairings or generates new pairings to enable crewing of the disrupted schedule. Similarly, pairings from a previous period can be used as a "warm start" to increase regularity.

Manual pairing generation may be performed at any stage to cater for special requirements such as training or charters.

The user can change rules (legal or otherwise) to produce an experimental - what if - solution such that it can be compared to the current set of rules. This is useful if the company needs to provide comment to the regulators on proposed rule changes. This can also be used when negotiating with Unions.

TPAC^TM Pairing uses advanced optimization technologies to minimize the total cost of crewing the given legs given the required constraints. Cost is defined as the actual cost (crew pay, hotels, allowances, transfers etc.) plus penalties.

Penalties are set by the user, enabling them to choose the trade off between various rules. There are several classes of penalties:

• Penalties for pairings that are not robust.
• Penalties for solutions that are inequitable between bases.
• Penalties for pairings that are legal but undesirable from the perspective of the crew.

Advantages of TPAC Pairing

The TPAC^TM Pairing Optimizer has the following advantages:

Produces robust patterns through:

• Minimization of vehicle changes.
• Penalties for tight connections.
• Penalties for duty time or operating time close to legal maximums.
• Minimization of number of pairings if variable crewing is required on each leg.

Flexibility:

• Optimizers can generate an entire solution, improve existing solutions or repair solutions after schedule changes.
• Extraction and optimization of weekly and daily schedules is available to improve solution regularity.
• Users can direct the optimizers using additional constraints if desired.
• Support of ground travel from base to alternate ports/stations or between nearby ports/stations.
• Support of international time zones and currencies.

User Interface

The user interface (TPAC^TM Workbench) allows the user to perform a number of optimization runs each with different run parameters and to then compare the results. Multiple simultaneous runs can be performed, and run progress can be monitored in real time. Runs can be scheduled to maximize the usage of available hardware. Runs can be monitored with "live graphs" to assess the quality of a solution before the run has completed. Results from an optimization run can also be edited to create a final solution or to "warm start" another optimization run.

Performance

Our optimizers are suitable for large problems that are made up of thousands of staff. Our technology can be scaled up on multiple CPUs and/or machines through the use of threading and scheduling.

Architecture

TPAC^TM Pairing is a Unix based technology that harnesses the power of FICO's Xpress optimizer. TPAC^TM Pairing is made available through the TPAC^TM Framework that includes:

• TPAC^TM Workbench -- A Java-based graphical user interface designed to support analysis, editing and interaction with our optimizers on any desktop environment.
• TPAC^TM Connect -- A web enabled remote access and systems integration platform.
• TPAC^TM Rules -- A common rules repository designed to assure consistency of business rules across the enterprise.
• TPAC^TM Reports -- A reports package with a library of common charts & metrics that can be customized and expanded upon.