Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.05. Home-Based Other Model Estimation5.1 Sample SizeThe final dataset used for estimating the HBO mode choice model consisted of over 14,000observations, of which a total of 12,404 were available for estimation. The excluded recordsinclude intrazonal trips, records where the chosen mode was transit but no transit path wasavailable and records with a highway in-vehicle time longer than 60 minutes. Table 5.1 showsthe number of observations by chosen mode. A common rule of thumb suggests that at least300 records per mode are required to obtain robust estimation results. For this reason, local andexpress bus modes were collapsed into a single transit mode, and park & ride and kiss & ridetransit access modes were collapsed into a single transit access mode. Table 5.1 also shows themodal shares, i.e., the weighted number of observations. Please see Section 3.3 for anexplanation of the weight factors. All estimation results were derived using estimation weightfactors, as corresponds given that the sample is choice-based.Table 5-1 Home-Based Other Sample SizeMode ChosenNo. ObsModalShareDrive Alone 4520 39.60%Shared Ride 2 3806 33.35%Shared Ride 3+ 2992 26.21%TransitWalk 1062 0.82%Drive 24 0.02%Total 12404 100.00%Modal shares are weighted proportions.5.2 Estimation ResultsThe final multinomial coefficients for the Home-Based Other mode choice model are shown inTable 5.2. The in-vehicle time coefficient is well within the typical range for home-based nonworkpurposes. Composite variables were used to obtain reasonable out-of-vehicle and costcoefficients. In the unconstrained models, the in-vehicle time or the cost coefficients werepositive (see runs #38 and #29 in Table 5.2). To constrain the cost coefficient, a value of timeof $3.00 was chosen, given that the HBO value of time is typically about 50% of the HBW valueof time. As in HBW, parking and auto operating costs are not shared among a vehicle'soccupants (this applies to the shared-ride modes). Parking costs were based on hourly rates fordowntown zones. An out-of-vehicle time to in-vehicle time ratio of 2.0 was used to construct acomposite out-of-vehicle time variable. This ratio is typical for HBO models.The mode-specific constants are based on the auto ownership properties of the home. Theyshow that, all else equal, drive-alone is the most preferred option, followed by the shared-ridemodes, with the transit modes as the least preferred across all auto ownership categories. Thisis indicated by the decreasing value of the bias constants (when ordered drive alone, shared ride,transit) within each market segment.Mode Choice - Home-Based Other Model Estimation 23