Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.0A measure of impedance more intuitive than logsum is either distance or travel time. Table 3.2shows observed and estimated average travel distance and travel time for each trip purpose andtime period, obtained with the base year model highway skims and person trip tables. TimebasedTLFD functions are shown in Figures 3.7 to 3.12. The comparison between observed andestimated trip length is not as close as normally observed when the gravity models are calibratedon the basis of highway travel time (or distance), because neither highway travel time nordistance include transit cost or transit travel time, while the logsums do consider all modes.However, given that the predominant mode in the OKI/MVRPC region is auto, it is expected thatthe model should estimate well average highway distance and travel time. As shown in Table3.2, for most purposes the estimates are within 10% percent of the observed values. Theseestimates were constructed excluding intrazonal trips, given that the model makes noassumptions about intrazonal travel times.Table 3-2 Average Highway Travel Time and Distance, OKI RegionTrip PurposeTravel Distance (mi)Travel Time (min)Observed Estimated % Error Observed Estimated % ErrorHBWPeak 11.7 12.7 8.5% 23.6 25.2 6.8%Off Peak 10.2 9.7 -4.9% 15.1 14.8 -2.0%HBOPeak 6.0 7.3 21.7% 12.8 16.0 25.0%Off Peak 6.2 7.1 14.5% 10.3 11.6 12.6%NHBPeak 6.0 5.8 -3.3% 12.0 11.7 -2.5%Off Peak 5.6 5.1 -8.9% 8.8 8.2 -6.8%Figure 3-7 Travel Time Trip Length Frequency Distribution Functions, HBW Peak4%3%Trip Frequency (%)3%2%2%1%ObservedEstimated1%0%0 10 20 30 40 50 60 70 80 90Travel Time (min)Trip Distribution - Gravity Model Application 22