Once you have initiated the model run by using the Toolkit function, the system will complete the following process to select street segments for rehabilitation:
Prior to running the model, the system will make sure the Budget setup tables are complete. These are required for the model runs to be processed. If all necessary data is not entered into these tables, you will receive an error message informing you which data is missing when you begin the model run. For additional information on these required fields, please see the Budgets help guide.
If you chose "Yes" in the prompt to update the supersegment current ratings, the system will first loop each supersegment through the system with all of the gathered Subsegment, Segment, and Field Inspection information so that the current conditions of the supersegment can be updated. This ensures that the best possible data will be used for the model runs.
Then, the model run will begin by creating a record for every supersegment in the filter set for the selected model year.
The system will set a Supersegment's PCI to 100 if no other PCI is defined. This allows Supersegments with no field condition inspection information to be included in the model runs.
The system then adds streets from the Planning Table to the model run. This includes all Year to Work and Year to Add segments. It will keep adding all forced street selections for that model year regardless of how much money remains in the budget.
These segments are marked as "Forced Selections" and the associated Rehab and construction costs will be calculated. If the supersegment is found in the "Year to Work" Planning Table for a future model year and is designated as having "No Rehab Selected Before" the forced year to work, the supersegment will be marked as a "Forced Skip Selection". This helps the user understand why this segment is being skipped in the current model year.
It will then determine the appropriate order for each forced selection by using the Maintenance Sequence fields in the Rehab Techniques and Rehab per Pavement/Classification modules. The system will calculate the remaining budget after the forced street selections have been rehabilitated.
The system tracks rehabilitation group budgets for the streets selected in the Planning Table.
These rehab groups are set for similar rehab techniques in the Rehab Techniques and Rehab per Pavement/Classification modules. They correspond with the % Budget set in the Budgets module.
The model next starts processing all supersegments that were not affected by the Planning Table.
For every supersegment (whether it will eventually be selected or not), the model fills in the basic model information including length, area, surface type before maintenance, classification, the PCI at the start of the analysis, the total curb and sidewalk length, the total number of driveways, the total patching estimate, and all of the load factor ratings. (Updating Initial PCI Values.)
If the supersegment has a value in the Override PCI field, it will override both the blended and controlling PCI values (found in the Supersegment module, Condition tab).
The program then goes through every supersegment in the model and calculates the next year's PCI value (assuming that it is not selected) and writes that value to the table. (Calculating deteriorated PCI values)
The program next goes through each supersegment and determines if it falls into any rehabilitation method. Based on this analysis, the following information will be written to the table: The rehabilitation method selected, the rehab sequence number, whether or not the PCI was in the Key Zone, and the Rehab Group. In addition, Restoration Points, Minimum Life, Next Rehab Year, and all costs are calculated and written to the table. (Selecting Recommended Rehab Methods)
With the remaining budget amount (if any), and going in Rehab Sequence Order (ascending) and then by order of Supersegment Priority (descending) the system will select streets for rehabilitation using the following process: (Selecting Segments for Rehab)
Note: It is possible that your model run could use all of the funding set aside for the forced selections so that no additional budget is available for other streets in your network.
The system will identify streets with a PCI between the minimum PCI and breakpoint PCI. These streets are considered to be in a Key Zone and are given a higher rehabilitation priority. These streets will be selected for rehabilitation at this time. (Processing PCI in Key Zone)
If any budget remains after the Key Zone streets are rehabilitated, the system will identify which additional streets should be rehabilitated to achieve the average system PCI (and required factor ratings). The priority order for the remaining streets to be selected for maintenance is determined by the Maintenance Sequence fields in the Rehab Techniques and Rehab per Pavement/Classification modules. (Processing PCI <= Breakpoint).
As each supersegment is processed for possible selection, the program also determines if it is part of a Linked Supersegment. If so, then the total cost of that segment and all supersegments linked to it is determined first. If the budget can handle the grouped supersegment costs, then that supersegment and all linked supersegments are selected. Each Supersegment selected as a Linked Supersegment will retain its selected rehabilitation technique (Linked Supersegments do not need to have the same rehabilitation techniques). The total cost of rehab for all Linked Supersegments is then subtracted from the total remaining budget and the system continues to select segments.
The above process will continue until the budget runs out of money or the average minimum PCI level has been reached.
The system will then calculate backlog costs, recalculate and update PCI values, update factor ratings, and update the results tables (STMODLYEAR) so that the user can see a summary of the final yearly totals. Backlog Costs sum up the costs of all supersegments that were in Key Zones that were not selected for rehabilitation.
If there is another model year to run, the model writes all of the supersegment values at once into the STMODLSEG table. If the supersegment had been selected in the previous year, then it uses the PCI, surface type, and ratings after selection. If it was not selected, then it uses the current values and Post PCI if not selected. Then the model starts over by again analyzing Year to Add Segments and Year to Work Segments, etc.
If a selected supersegment has a Restoration Point set, then the new PCI will be calculated as the current PCI plus the Restoration Points. If there are no Restoration Points, then the system uses the Default Reset PCI (as defined in the Rehab per Pavement/Classification module).
If the selected rehab technique had a Minimum Life set in the Rehab per Pavement/Classification module, then the next year that the segment can be selected for rehabilitation will be the year after the budget year plus the minimum life.