Routing, Rating and Scheduling a load with an empty stop

Special handling is required for loads containing empty stops for one or more of the following reasons:

Load routing requires that an associated trailer equipment type not travel empty between the first pickup and last delivery. A load having zero shipments attached violates this condition unless special conditions are applied.
Empty stops will not be filled by the optimizer unless doing so results in a savings of the overall solution cost. All pre-built loads, including those having empty stops must rate successfully in order to establish a baseline freight cost. If no cost can be computed, re-planning will not update the load. This baseline cost is compared to all planning options for available shipments and shipments will only be added to a pre-built load when doing so reduces the overall solution cost. If all rates are strictly distance-based (for example), zero load quantities do not present a rating problem. However, quantity-based rates can be defined for carriers. If defined, these rates must also be considered against loads with empty stops.
Lastly, scheduling determines stop-level arrival and departure times partly based on loading or unloading that needs to occur along the route. When variable loading/unloading rates for a shipping location are quantity-based and stop quantities are zero due to empty stops, it could result in a terribly skewed, or even a violation of a shipping location’s business hours of operation somewhere at any point along the route.

Dummy shipments

To support the ability to route and rate, and to reduce scheduling issues for loads containing one or more empty stop, both the optimizer and Routing, Rating and Scheduling (RR&S) processes formulate dummy shipments to temporarily fill empty stops on pre-built loads fitting the definition of Skeleton Load or Pre-booked Capacity.

When pre-built loads are input for re-planning, the stop sequence of these loads are examined and if any stop is found to have no shipments attached, a dummy shipment is created and attached to the stop. The following examples illustrate how dummy shipments are applied to a load having one or more empty stop.

Example 1: Empty skeleton load

Stop Sequence	Stop Type	Shipping Location	Shipment
1	Pick	Detroit	None
2	Pick	Cleveland	None
3	Drop	Pittsburgh	None

Dummy shipments are temporarily attached to empty pick/drop combinations to assure each stop has at least one shipment:

Detroit – Pittsburgh
Cleveland - Pittsburgh

Example 2: Partially empty pre-booked capacity load

Stop Sequence	Stop Type	Shipping Location	Shipment
1	Pick	Detroit	SH-1
2	Pick	Cleveland	None
3	Pick and Drop	Pittsburgh	None
4	Drop	Philadelphia	SH-1

In this case, one dummy shipment is temporarily attached to assure each stop has at least one shipment:

Cleveland – Pittsburgh

The following optimization parameters are used to set default quantities used for rating and scheduling for all dummy shipments. Values must be set for quantities where the type is used to compute freight costs or is a factor in computing variable loading / unloading times at shipping locations.

DummyShipmentWeight (in the system unit of measure)
DummyShipmentVolume (in the system unit of measure)
DummyShipmentPieces
DummyShipmentSkids

How dummy shipments support the ability to route a load

Temporarily filling empty stops with dummy shipments virtually removes the case where a load becomes empty after the first pickup and before the last delivery and opens the opportunity for the optimizer to alter the input stop sequence to achieve even greater cost savings in the overall solution.

Note: Optimizer is not permitted to re-sequence skeleton stops. However, skeleton stops may be re-sequenced manually.

How dummy shipments support the ability to rate a load

Dummy shipment quantities are used to rate a load when the eligible rate is based on shipment quantities. This allows for computation of a reasonable internal freight cost that is used as the baseline for determining if an overall solution cost savings can be realized by replacing the dummy shipment(s) with currently available shipments.

How dummy shipments support the ability to schedule a load

For skeleton loads, dummy shipments attached to an empty skeleton stop are not a factor in scheduling. This is because skeleton locations define an estimated service time for the stop. When the stop has no actual shipments attached, this skeleton location element is applied. When the skeleton stop has shipments attached, then the actual shipment attribute will be used if the shipping location defines a variable loading/unloading time.

For pre-booked capacity loads, dummy shipment quantities are used when a shipping location defines a variable loading/unloading time for that shipment attribute.