Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.0• For model calibration and validation purposes, commercial four-tire trucks trips cannot beseparated from non-commercial autos and four-tire trucks. All of the traffic count surveysavailable for this study classify four-tire trucks in the same category as passenger cars, based ontheir lengths and number of axles. Automatic traffic recorders cannot distinguish betweencommercial and non-commercial pickup trucks, sport utility vehicles and vans.2.1.4 Truck countsTruck classification counts are essential to the SME calibration procedure. There are no standard tests bywhich to measure the validity or certainty of trip matrices resulting from the synthetic matrix estimation.Correctly applied to robust count data, the process will result in close fits with observed countsirrespective of the number of counts. The more counts included, the more constraints imposed on theprocess and the narrower the range of candidate solutions.ODOT, MVRPC, OKI and the Kentucky Transportation Cabinet contributed available truck traffic counts,which were geo-coded to the links of the travel model network that was imported into TransCAD. Intotal, 890 unique count locations were input to the truck model GIS database. Table 2-1 summarizescount locations by county and network link functional classification.Table 2.1. Truck Traffic Count Locations by County and Network Link Functional ClassCoded Functional ClassCounty, State InterstatesMajorArterialsMinorArterialsMajorCollectorsMinorCollectors Ramps Xways TotalBoone, KY 16 11 10 37Butler, OH 8 27 10 17 8 70Campbell, KY 7 5 1 6 2 21Clermont, OH 7 7 11 21 5 51Dearborn, IN 0Greene, OH 9 22 21 5 21 6 84Hamilton, OH 92 60 13 3 98 6 272Kenton, KY 13 9 10 1 33Miami, OH 9 4 20 16 1 4 54Montgomery, OH 34 54 43 5 32 19 187Warren, OH 15 15 16 19 16 81Total 210 203 156 103 1 179 38 890For SME calibration, bi-directional average daily traffic (ADT) counts were split evenly between “AB” and“BA” link travel directions, which resulted in 1039 links with counts information. Of these, 841 links withcount information were used in the calibration process.Since the SME procedure adjusts the seed matrix based on the differences between assigned andcounted traffic on the shortest path between origins and destinations, counts should be located along theshortest paths between O-D pairs. Counts on network links which are traversed by many shortest pathsand which also carry higher volumes of truck traffic provide the most information to the estimationprocess. For example, an analysis of free-flow shortest paths on the truck network revealed thatapproximately one-sixth of the 25,905 shortest paths that connect the 161 FAZs use the network linksthat represent I-75 near the Warren-Montgomery County line, links which also carry a relatively highvolume of truck traffic. For comparison, I-70 also carries a high volume of truck traffic, but due to theshape of the study area and the zone system far fewer O-D interchanges use the I-70 link as a shortestpath.Truck Model - Base-Year Truck Model Development 10