For the heuristic algorithm, PR-TT selects the first job in the sorted list and only calculates the scores for this job paired with each truck. This determines the best truck for the selected job. If there are non-uniform trucks in a pool, PR-TT selects the twinned jobs first, which reserves or dispatches the twin capable trucks earlier to discourage dispatching a twin capable truck to a single job later.
However, before calculating the scores for the selected job, PR-TT performs various checks that are similar to the checks done for the global method. PR-TT does not execute some of these for non-idle trucks or dedicated vessel or rail pools. If a check fails, then the TT is skipped. The following table lists the checks performed:
|
Validation |
Idle trucks only? |
Excludes dedicated vessel or rail pools? |
|---|---|---|
|
If the CHE is capable of handling the job (includes checking both twinned or paired jobs if the work instructions are twinned or paired). |
No |
No |
|
For paired jobs, if lateness exceeds a non-user-configurable threshold, PR-TT uses the same formula as the global method for lateness. If none of the trucks in the TT list pass this check and the capability check above for a paired job, then PR-TT separates the pair and considers each of the units individually. PR-TT never separates twinned jobs, though. |
No |
No |
|
If the job violates POW MaxPMs limits. |
Yes |
No |
|
If there is a prior load move that is not dispatched or not being carried yet. |
Yes |
Yes |
|
If the job is too far ahead in the sequence based on the EC parameters GLBSQO and GLBSQY. |
Yes |
Yes |
|
If the job violates yard crane MaxPMs limits. |
Yes |
Yes |
|
If the job has an invalid travel time. |
No |
No |
|
If the job is too early for the TT. |
No |
Yes |
After all of the above validity checks are made, PR-TT performs some additional checks while calculating the score for the selected job against each truck. If any of the checks fail, then PR-TT removes that job and truck pair from consideration. The following table lists the steps that PR-TT executes for the selected job against each truck while adding any calculated costs, scores, or penalties to the final score at the end.
The following checks and calculations are the same as with the global method. For more information, see 9a. Calculate scores for the global method (on page 1). In addition, PR-TT does not execute some of these for non-idle trucks or dedicated vessel or rail pools.
|
Validation/Score |
Description |
Idle trucks only? |
Excludes dedicated vessel or rail pools? |
|---|---|---|---|
|
Travel cost |
Determines travel cost using the travel time from the last position of the truck. |
No |
No |
|
Lateness score |
Determines lateness, which is one of the main factors in score calculation. Penalizing a late move is critical during this process. To calculate the lateness score, first PR-TT calculates the lateness time in seconds. Once lateness time is calculated, PR-TT calculates the lateness score. However, PR-TT also checks how late the truck will be based on lateness time. If the truck will be really late, then PR-TT calculates double the excess lateness based on a threshold and adds this to the lateness score. This ensures that very late jobs are dispatched as soon as possible by exaggerating their scores. Lateness time is capped at 600 seconds. (DOC-2453) |
No |
Yes |
|
Max travel distance penalty |
Determines if a max travel distance penalty applies and the value of this penalty. If the travel distance from the truck's position to a job exceeds 600, then the max travel distance penalty applies, otherwise the penalty does not apply. The value of 600 is not user-configurable. |
No |
Yes |
|
MaxPMs violation penalty |
Determines if a MaxPMs violation penalty applies. PR-TT is allowed to exceed the MaxPMs limit of a POW by one dispatch. If the truck and job pair under consideration is dispatched and exceeds the MaxPMs by one, then PR-TT adds a penalty equal to the value of the EC parameter GLBMMV. |
No |
Yes |
|
Prioritized job score |
Determines the prioritized job score for prioritized jobs. This score is a negative value to make the prioritized job more attractive. If the job is prioritized, PR-TT adds -80 points to the score. The point value is not user-configurable. |
Yes |
Yes |
|
Min moves violation penalty |
Determines whether a negative penalty is added to the job to make the job and truck pair more attractive to attempt to meet the MinPMs limit for the POW. If the number of dispatched jobs in POW plus the job order number in the work queue for the job being considered is less than or equal to the MinPMs limit for the POW, then PR-TT adds a negative penalty to make this truck and job pair more attractive. |
Yes |
Yes |
At the end of these calculations, PR-TT calculates the total score for the selected job and truck pair under consideration. PR-TT executes the above steps for all of the applicable trucks paired with the selected job. Based on these scores, PR-TT determines the best truck for the selected job and sends that to the dispatching mechanism.
Unlike the global algorithm, which creates a scoring matrix to decide the best job and truck pair for all possible job and truck pairs together, the heuristic algorithm only looks at one job at a time. Therefore, PR-TT calculates the best truck for a job, reserves or dispatches that job, then calculates the best truck for the next job, and so on. For the heuristic algorithm, PR-TT decides the best truck for each job separately.