At the end of the process, audit checks are undertaken to assess any changes are justified and the estimates can be finalised and entered into the database.
The estimate update can either be an annual process or be updating estimates from several years depending on how well they have been maintained. The first scenario may require less oversight if effort has been maintained historically. If the estimates are out of date, many updates maybe required, and these may change the previous estimates quite significantly. This may have implications for measures such as network vehicle km travelled (VKT) or ONRC/ONF categorising. Therefore any significant changes in estimate from previous values should be checked and confirmed as appropriate. Suggested checks include:
- Has the current estimate differentiated from the previous estimate by more than the maximum of 50 vpd or 10%?
- The 50vpd threshold accounts for low volume roads where 10% may only equate to say two vehicles per day for an estimate of 20 vpd.
- Confirm if any carriageway sections (that should have been updated if part network updates) have a current estimate
- Note the check is against carriageway sections rather than links. Some carriageway sections may miss being updated if they are inadvertently not assigned to a link.
- The update process may only serve arterial routes so check all arterial carriageway sections have an update estimate
- Check the estimate data is complete
- This includes estimate date and the estimate AADT is not blank or set to 0
- Check there is just one estimate record for the year (while not critical it does keep things tidy)
- Check any estimates that seem out of alignment with surrounding estimate or do not reflect the asset managers understanding of the network
- Check count against Pavement Use category and ONRC/ONF category
- Flag sections that have an estimate more than one ONRC/ONF classification away by volume definition or where the section is outside the assigned pavement use band.
- Check where the percentage of heavy vehicles has changed by more than 3% from the previous estimate and that the change is justified
- Check traffic mix percentages all add to 100% and no fields are null
- Check that the percentage cars is the highest category.
Once these checks are completed, the estimates are ready for loading into the database.