Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.0estimation results when the submodes are considered separately. Specific local and express busconstants will be computed during model calibration.Similarly, the original drive-to-transit access modes, park & ride and kiss & ride, were collapsedinto a single mode, drive-to-transit, because there is no difference in the utility equation betweenthe two modes, other than the constant term. Normally, these access modes differ due to theparking cost incurred by the park & ride choice; however, in the present case all park & ride lots(in the base year) are free. Specific park & ride and kiss & ride constants will be computedduring model calibration.4.2 Estimation ResultsNearly 100 estimation runs were conducted in the search for an appropriate HBW mode choicemodel. A complete listing of all runs is available in Appendix 1. Table 4.2 shows the bestmultinomial model estimated, and others that serve to illustrate the estimation process. The bestmultinomial model exhibits significant coefficients on all variables (i.e., t-statistics greater than1.8), with coefficient values within acceptable ranges. In particular the in-vehicle time coefficientis expected to be in the [-0.02 to –0.03] range. The rho-square statistic, which may beinterpreted similarly as the R 2 statistic in a regression model, is typical for mode choice models.For this model, costs were not apportioned among the occupants of a carpool, consistent withrecent findings that indicate that most carpools are composed of members of the samehousehold. The coefficient of transit drive access time was specified to be equal to the in-vehicletime coefficient.The implied value of time for the region is approximately $7, which is somewhat higher thanexpected given the region's average income. 2 The ratios of out-of-vehicle to in-vehicle time areall reasonable and within acceptable ranges, and are comparable to results obtained in other U.S.metropolitan areas. The walk access variable has a relatively high coefficient, possibly the resultof using centroid link times in lieu of actual walk times in the estimation file 3 .The model was stratified by market segments defined as a function of household auto ownershipand the number of workers in the household. The estimation results corroborate reasonableexpectations regarding modal usage among people in the various market segments. Forexample, there is a higher likelihood of transit usage and ride sharing among workers in zeroauto households and workers in households with less cars available than workers. Similarly themodel indicates that the likelihood of choosing transit decreases as the ratio of cars to workersincreases.Run #79d was one of several attempts to separate transit wait time into two components: waittime if 10 minutes or less and additional wait time. The rationale is that the first 7 to 10 minutesare the true actual wait time, while the additional time represents the inconvenience ofinfrequent service. The reasoning behind the 7-10 minute figure is as follows: people who useroutes that run headways of 15-20 minutes do not normally pay much attention to the schedulewhen planning their trip, and so on average incur a wait time equal to one half the headway,2 The home-based work value of time is expected to be approximately 20% to 30% of the averagehousehold hourly income. According to the 1990 CTPP, the average household income in the OKI RegionalCouncil region is $38,379, which results in a household hourly rate of $18.45. Adjusted for inflation, in$1995 the value of time should be expected to be approximately between $4.3 and $6.5 per hour.3 A better measure of actual walk times can be computed when the trip origin and destination coordinates(latitude and longitude) are available in the Home Interview and On-Board Surveys.Mode Choice - Home-Based Work Model Estimation 18