Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.0Bias factors to account for the omission of unidentified TAZ or external station trip ends were recalculatedby Parsons Brinckerhoff after the MVRPC and OKI model networks were consolidated. These new biasfactors were applied to each record.External station correction factors were developed to account for trips that were originally coded asexternal, but were found to actually be trips between the OKI region and the MVRPC region thattemporarily left the study area through one external station and re-entered through another. This wasparticularly a problem for trips between some Butler and Montgomery County stations and between someWarren and Greene County stations. The multiplicative factors were calculated as the expanded numberof actual external truck trips divided by the expanded count total of external truck trips. This reduced thenumber of actual EE and IE trips at certain stations. For trucks, the correction factors applied during theexpansion process are shown in Table 2-4.Table 2-4. External Station Correction FactorsRoute TAZ Station ODOT Station EE factor IE factorSR 503 N 2449 1044 1.000 0.893SR 725 W 2511 872 0.922 0.720US 35 W 2512 873 0.968 1.000Route TAZ Station ODOT Station EE factor IE factorI 71 N 2446 1024 0.997 0.988SR 73 E 2447 1025 1.000 0.987SR 72 S 2508 856 0.861 1.000US 68 S 2509 857 0.873 0.903SR 380 S 2510 858 0.886 0.556The ODOT Surveys were conducted in only one direction at each external station, mostly in the outbounddirection, except at four stations in Miami County where the surveys were taken in the inbound direction.To use these data to form trip tables, the technical memo recommends an assumption of symmetry; thatis, an i-to-j trip in the survey direction implies a j-to-i trip in the non-survey direction. To implement this,EE trips were multiplied times one-half, so as not to double count, because they are theoreticallysurveyed at two external stations. For IE trips at outbound survey stations, the opposite direction factorwas used to derive the number of EI trips between the same external-station-TAZ pair. The equivalentsteps were taken for the four stations at which surveys were taken in the inbound direction. The ODOTopposite direction factor is the total number of trucks counted by the automatic traffic recorder in bothdirections, divided by the total number of trucks counted in the survey direction. For example, if theopposite direction factor for a particular station’s survey records is 1.95 and 20 expanded trips were to bemade in the survey direction, i-j, then the opposite direction factor implies that 19 trips would be made inthe non-survey direction, j-i.The ODOT technical memo noted that only one truck was surveyed at Station 842 (Consolidated TAZ No.2494), I-70 east of I-675 interchange. To remedy this, the technical memo suggested using the trip endssurveyed at other stations that named Station 842 as the trip origin as an indicator of EE trips for Station842, resulting in 7,777.99 EE trips. For IE and EI trips, the memo recommended using the tripinterchanges found in the surveys of passenger vehicles and expanding these interchanges to theproportion of total vehicle traffic that the automatic traffic recorder counted as trucks. This produced asynthesized total of 13,308.46 IE plus EI truck trips. An additional correction factor of 0.615606 wasTruck Model - Base-Year Truck Model Development 13