The process of computing these factors is time consuming and labor intensive, but more importantly the accuracy of these factors are of greater concern. Some (but not all) of the reasons for their inaccuracy are:
they are not computed each year and therefore become outdated
there is no written procedure used to compute the factors which may cause inconsistent calculations
the traffic within the large planning districts may not be homogeneous causing some highways to be over- or under-designed
increases in the population are not considered
the Average Daily Traffic (ADT) is averaged over the entire state for each functional class
the rural traffic in counties that have a Municipal Planning Organization (MPO) may not be adequately considered - there is no procedure for handling the factors near the DOT/MPO interfaces
there may be other important variables that are not considered in the computations.
Therefore, research is needed to develop and document a procedure and recommend software for computing 20-year traffic forecasting factors. The results of this research should improve the Departments confidence in the accuracy of its traffic forecasting.