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

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 utilisation must be maximised, however, so they cannot stand idle while their crew takes a break. For such equipment, it is necessary for crew to be paired 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, then 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 other may also include duties such as training, shunting, standby duty etc.

A good set of crew pairings has the following characteristics:

TPAC Pairing automatically creates a set of optimised crew pairings for schedules that are too large for manual pairing creation. It ensures that the crew pairings have a minimum cost subject to the constraints given by the crew work rules and the desire for a solution that is robust to disruptions.

It can be used in several ways:

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

TPAC Pairing uses advanced optimisation technologies to minimise 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.

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

A range of standard reports give key metrics to enable evaluation of the quality of solutions.

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.

Information for ports/stations can be downloaded or maintained locally:

Crew requirements from carry-in pairings starting in the previous bid period are subtracted from the required crew. Manual pairings are then optionally generated to cater for any special requirements (e.g. training, special charters), and the crew for these is also subtracted from the required crew.

The schedule is then prepared for optimisation. This may involve extracting a weekly schedule containing those legs that are repeated every week for the schedule period, and a daily schedule containing those legs that are repeated for most days of the schedule period. Separate problems are prepared for each crew type - e.g. a separate problem for each fleet that requires different skills to operate it.

Extra legs may be added to the schedule for travel using the services of other companies for paxing/deadheading purposes.

If maximum schedule regularity is desired, the global optimiser is used to produce a solution for the daily problem, which is then improved using the local optimiser. Pairings from the daily solution that match well with the weekly schedule are fixed in the weekly solution, and the remaining legs in the weekly solution are then used as the weekly problem to be solved. The weekly problem is then optimised using the global optimiser, and this solution is improved using the local optimiser.

A similar process to the above generates a solution for the entire bid period using the weekly solution as a starting point. For schedules with insufficient daily regularity, optimisation can start by solving the weekly problem.

If regularity is not important, the schedule for the entire bid period may be generated in one step, omitting the daily and weekly steps.

The resulting optimised solutions then have pairing numbers assigned to each pairing, after which reports are printed and the result is exported to the pairing assignment system.

The optimisation process can be started or restarted from any point. The optimiser can be directed by changing the amounts of penalties applied to undesirable pairings, or by adding in required, prohibited or suggested connections.

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 finalised a few days in advance of the start of the block. This process is repeated each day.

In this case, information about each crew member's preferences, work history and assigned work days is also provided to the system. The optimisers then assign pairings to individual crew members at the same time as pairings are generated. This allows the preferences of the crew members to be taken into consideration when generating the pairings.

To increase the speed of the optimisation process, only a small number of days in the future are considered in these problems. Also, the previously planned pairings are used as suggestions to the optimiser.

On the day of operations, planned pairings may be disrupted by delays and cancellations. TPAC Pairing automatically detects which pairings are now illegal, and modifies existing pairings or generates new pairings to enable crewing of the disrupted schedule.

The user interface enables initiation and monitoring of optimisation runs, review of solutions and interactive pairing creation or modification.

Interactive pairing creation and modification is performed using a graphical editor. Many options are available for selection of displayed ports, legs and pairings to reduce screen clutter. Pairings are colour coded from a selectable palette. Clutter is also significantly reduced by the optional dynamic display of legs suitable for adding to the pairing as the pairing is built.