2.12 Orders

1. Locations

   The pickup and delivery locations must be given for each order and must match a location identifier defined in the set of locations. (See Section  2.10.)

2. Times

   1. Earliest and Latest Times

      The earliest pickup time is the earliest time that the order will be available at its pickup location. The earliest delivery time is the earliest time the same order is able to be delivered. This is analogous for latest times.

   2. Time Windows

      The times when an order can be picked up and delivered can also be specified by time windows. If both earliest and latest times and time windows are specified, then both must be satisfied for the order to be picked up or delivered.

   3. Service Time

      Each pickup and delivery may have an amount of service time associated with it. This is the amount of time incurred by the vehicle when the order is picked up or delivered. This time is in addition to any site, load or unload time incurred because of the location or vehicle.

3. Soft Time Window Penalties

   If an order has soft time windows then both fixed and variable penalties are incurred if these time windows are missed.

   1. Fixed Penalty

      A constant penalty that is incurred if the soft time windows are missed. Note that if multiple soft time windows are defined, this penalty is still only incurred once.

   2. Variable Penalty

      A penalty incurred per minute the time window is missed. If multiple time windows are present, it is calculated based on the nearest soft time window boundary.

4. Maximum Duration

   Orders can optionally have a maximum duration specified. The optimiser will not generate solutions that assign such orders in a way that the time needed to service them exceeds their maximum duration. (The duration of an order is defined to be the time that elapses from when its pickup commences up until the time when its delivery is complete.)

   Note that if the minimum service time needed by an order exceeds its maximum duration then the order cannot be assigned by the optimiser.

5. Weight and Volume

   The weight and volume of the order are given in arbitrary units which must be consistent with the respective vehicle capacities previously defined. For example, the volume may be measured in cubic metres, number of pallets or roll cages.

6. Assign Cost

   This is a (monetary) cost associated with servicing the order. This can be used to prefer certain orders as the optimiser will attempt to find the solution with lowest cost. Negative costs can also be used.

7. Hidden Assign Cost

   The hidden version of the assign cost. While this is used in the computation of a solution, but it will not be seen in the final output.

8. Vehicle-Specific Assign Cost

   An order can have costs associated with it that are only incurred when the order is assigned to a specific vehicle or set of vehicles. These costs are incurred in addition to any assign cost for the order.

9. Vehicle-Specific Hidden Assign Cost

   An order can have hidden costs associated with it that are only incurred when the order is assigned to a specific vehicle or set of vehicles. These hidden costs are incurred in addition to any hidden assign cost for the order.

10. Preferred Vehicles

    An order can have a list of preferred vehicles. A reward is obtained on assigning the order to one of its preferred vehicles. This reward is calculated using a fixed reward, a volume dependent reward and a weight dependent reward. See Global Parameters for an explanation of these rewards.

11. Order Precedences

    Two orders can be associated with a precedence. This requires that the delivery of the first order must be completed before the pickup of the second. An optional duration that must elapse between the delivery and the pickup can also be specified. This duration is called the gap.

    Precedences are often used to model cross-docking, where the first leg of the order must be delivered before the second leg can commence.