Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.0The internal-external trip production equations (at each internal zone i) take the followinggeneral form:IE Trip Pr odctionsi= β ∗ Populationi+ γ ∗ Employment iThe coefficients of this equation were estimated for each cordon location strata using OrdinaryLeast Squares estimation. Zones not reported in the cordon survey were assigned zero tripproductions, instead of setting them to missing values. The results of the estimation aresummarized in Table 8.12. Note that, as expected, the closer a zone is to the cordon line thehigher the trip rate per inhabitant and per job is. In all cases the coefficient estimates for and are statistically significant and have the correct signs, indicating that increases in zonalpopulation and employment result in higher internal-to-external trip productions. The R 2reported in Table 8.12 has been redefined to account for the zero intercept. The models may beimproved by stratifying them, for example into work and non-work trips, and using variables suchas retail employment or retail square footage to explain non-work trips.A few zones were excluded from the estimation dataset because they appeared to be outliers.The criteria for excluding individual zones were defined based on residual plots, and are asfollows:• Central Cincinnati (cloc=1), exclude ifo Population greater than 3,500 and less than 100 trips reportedo Population greater than 2,300 and more then 400 trips reportedo Population less than 1,000 and more then 250 trips reportedo Employment less than 1,000 and more than 400 trips reported• Central Dayton/Xenia (cloc=7), exclude if population less than 500 and more than 500 tripsreported• Intermediate Zones (cloc=2), exclude ifo Population less than 1,500 and more than 500 trips reportedo Population more than 6,000o Employment less than 4,000o Employment less than 1,500 and more than 600 trips reported• Close to the Cordon Zones (cloc=3), exclude ifo Employment greater than 3,000o Population greater than 4,500o Population greater than 1000 and more than 1,500 trips reportedo Employment less than 1,000 and more than 1,350 trips reported• Special Generators (cloc=5), exclude if Employment less than 2,500 and more than 2,000trips reported.Note that these criteria are completely empirical and would not necessarily apply with differentcordon location classifications, zonal aggregations or cordon survey dataset. The limits definedabove are merely a convenient way to exclude outliers and to document the reason for theirexclusion.Trip Generation - External Cordon Survey Analysis 51