Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.0OKI contributed a critical set of directional counts along the I-75 mainline between 23 interchangelocations, ranging from the Ohio River (US 50) to as far north as SR73 in northern Warren County, anadditional six locations on I-275, I-74 and US 50, as well as numerous ramp counts along these stretchesof freeway. These counts were taken in 1999 and due to their importance to the NSTI study and thesynthetic estimation procedure, it was decided that a “late-1990s” truck model calibration provided thebest chance of producing a working model from a relatively contemporaneous set of counts across thestudy region, despite of the designation of 1995 as the base year. Moreover, OKI and MVRPC staffexpressed concern over several geographic areas being under-represented in the calibration procedure, ifcounts were restricted to just a few years. For these reasons, counts taken from 1994 to 2000 were usedto estimate the base-year truck model. The counts summarized by county and year are shown in Table2-2.Table 2.2. Truck Traffic Count Locations by County and Year of CountYearCounty, State 1994 1995 1996 1997 1998 1999 2000 TotalBoone, KY 1 8 4 7 8 9 37Butler, OH 53 1 16 70Campbell, KY 1 11 5 4 21Clermont, OH 51 51Dearborn, IN 0Greene, OH 78 2 4 84Hamilton, OH 137 135 272Kenton, KY 4 3 7 14 5 33Miami, OH 54 54Montgomery, OH 129 14 44 187Warren, OH 57 24 81Total 266 1 66 194 25 218 120 890For SME calibration, the ideal truck count should cover a period of 24 hours, with separate hourly totalsfor each direction and broken down by vehicle classification. Few of the counts were provided in exactlythis form; therefore, link counts were adjusted as necessary to form daily, directional counts by SU andMU truck classifications. To do this, the following rules were applied:• Where the count was expressed as a bi-directional volume, this number was split evenly between“AB” and “BA” link directions. This affected a number of counts that were provided in the form ofADT summaries.• Where only the total number of trucks was provided or trucks as a percentage of total vehicles,judgment was made as to the functional class of the roadway and the proportions shown in Table 2-3were applied to derive SU and MU splits. This affected ODOT ADT counts and some of the countsprovided by the Kentucky Transportation Cabinet. In addition, these percentages were used toclassify truck types from the 1995 ODOT External Station Survey.Table 2-3. Expected Proportions of Multi-Unit Truck TypesFunctional ClassMU / (MU + SU)RuralUrbanInterstate 0.81Other Principal Arterials 0.60Minor Arterial, Collector, Local 0.42Interstate 0.71Other Freeways and Expressways 0.57Other Principal Arterials 0.56Minor Arterials 0.47Collectors 0.45Local 0.30Source: derived from Table 4.2 “Percent Distribution of Traffic by Vehicle,” QuickResponse Freight Manual, USDOT, 1996, p. 4-13.Truck Model - Base-Year Truck Model Development 11