Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.03.3 Estimation Weight FactorsThe available estimation sample is a choice-based sample: auto observations are taken from thehome interview survey, while transit observations are taken from the transit on-board survey. Aweight factor is applied during estimation to preserve the actual proportions of each mode in theregion. For auto trips, the factor is 1.0. For transit trips, the factor is calculated as the ratio ofthe number of transit observations in the home interview survey to the number of observations inthe on-board survey, and it is equal to 0.089.3.4 Highway Network Times and DistancesPeak and off-peak travel times were obtained from the Model 54 1995 highway networks. Peaktravel times were skimmed from the final (i.e. second-pass) loaded AM network. Off-peak traveltimes were skimmed from the free-flow network speeds. Terminal times were obtained fromModel 54. Intrazonal times are not used because the model estimation excludes intrazonal trips.3.5 Transit In-Vehicle Time, Out-of-Vehicle Time, and FaresExisting transit skims (from Model 54) were inappropriate for use in mode choice estimation forthe following reasons, related to the model structure itself and to data/program problems foundin Model 54 transit skimming routines:• The consolidated model considers drive access to local and express service separately, whileModel 54 considers drive access to the "best" transit service;• Bus run times are unreasonably high in Model 54, due to the use of observed counts in theestimation of congested speeds. As explained in Part II, in the consolidated model thesespeeds are capped to ensure they do not become unreasonably low;• Model 54 uses an inappropriate setup to build transit paths, which results in incorrect waittimes; and• Model 54 limits the maximum driving distance to transit stations to 5 miles, in most cases,and 0 miles for the stations/transfer centers at or near Cincinnati downtown.• Model 54 performs a limited search of walk access connectors, unnecessarily restricting thesearch for walk connectors when an acceptable highway connector exists.• Model 54 uses a "shadow price" for parking costs at park and ride lots, to capture thedifference between “formal” and “informal” lots. In the base year all P&R lots are “informal”,and since there’s no cost to park the estimation uses zero parking cost for the park and ridealternatives.The restrictions on creating walk and drive access connectors are troublesome because they mayartificially limit transit accessibility. For estimation purposes, it is preferable to let the modechoice model determine the likelihood that any given transit path is chosen (allowing the modelto consider paths that may appear unreasonable), than to let the path builder determine theavailability of these paths. One can reasonably expect that long transit drive access legs areuncommon in the data, and consequently the probability of driving to transit when one lives farfrom the station will be very small, if not zero. Similarly, setting the maximum drive accessdistance to zero for some stations precludes the option of being dropped off at the station. It ispreferable to let the mode choice model decide the likelihood of this behavior. In the case of thewalk access connectors, the model should consider all transit access points within reasonablewalking distance of a zone, regardless of whether a centroid connector already exists in thehighway network. The search should not be limited to the shortest walk connector, becausethese connectors may not necessarily result in the shortest transit paths.Mode Choice - Estimation File Preparation 14