Travel Demand Model

Population Synthesis

The Population Synthesis is developed through a statistical model that divides the number of households by income level, household size, and vehicle ownership. Secondly, the model utilizes statistical procedures to expand the data to match the totals based on individual data records and sample weights from household surveys.

Trip Generation

It determines how many trips will be produced in each model zone, as well as how many people will be attracted to each of the trip’s purposes. These characteristics include employment, vehicle ownership, and household size as they estimate the number of trips a person may make in one day.

Trip Distribution

Once the model recognizes the total number of trips beginning and ending in every subarea of the Washington metropolitan area, it must decide which pairs of TAZs those trips will move between (for each trip purpose). For example, if one hundred shopping trips begin at a TAZ, the model uses travel times estimated from the network file to find nearby zones where shopping trips are attracted and the TAZs match. Once every trip is matched, an origin-destination table is developed that shows the number of trips between each combination of TAZs. 

Mode Choice

Once people know where they are going, they must choose how to get there. If they own a car, they could drive, carpool, walk to transit, or park and ride. Based on the number of vehicles available in each household and TAZ attributes (land use, transit accessibility), the trips for each origin-destination pair are split among the various modes of travel. IS used A multinomial nested logit choice model that distinguishes between the three highway modes (SOV, HOV2, and HOV3+) and the four transit modes of access (Walk, Bike, Park-n-Ride, and Kiss-n-Ride) 

Trip Assignment

Route assignments in the model are determined by the number of vehicles traveling on the roadway network and where they are trying to go. Vehicles then try to find the shortest travel time to their destination. Each trip follows more or less the same route in successive runs. Based on the number of vehicles using each road segment and the capacity characteristics of that segment, the new travel speed for each road is updated.

Model Development

TransForM 2.5 – An Advanced Practice Dynamic Tour-Based Hybrid Travel Demand Model, introduces tour-based mode choice modeling and simulation-based Dynamic Traffic Assignment (DTA). This version also prepares an interface that adapts the MWCOG’s regional activity-based model, currently under development.

TransForM 3.0 – An Advanced Practice Dynamic Activity-Based Travel Demand Model, currently under development, is the final product that will include advanced techniques that are technically practical, cost-effective, feasible with respect to resources, and grounded in sound modeling theory. This pathway is not limited to coupling an activity-based tour-oriented travel forecasting model with a Dynamic Traffic Assignment component but will encompass the larger vision of how an activity-based tour-oriented demand model fits within the overall need for an analysis tool.

Beyond TransForM 3.0

The Prince George’s County Planning Department is committed to maintaining innovative modeling capabilities through the short term while working longer-term on converting or upgrading to TransForM with TransForM – Beyond 3.0: Custom Applications, Comprehensive Updates, and Technology Transfer.

This upcoming version of the model is an Activity-Based Tours-Oriented (ABTO) travel demand forecasting model that will create a new post-COVID version of the base year that will reflect the state of travel patterns and travel behaviors as we emerge from the pandemic. This post-COVID base-year-2022 will be informed by work products from BIG DATA sources and will include a detailed growth management software and analysis tool (GMSA) that will standardize the traffic impact analysis (TIA) procedures of new development at the parcel level of land property analysis.

TransForM includes the use of designated streets to the appropriate urban street design standards within the 2017 Prince George’s County Urban Streets Design Standards (USDS), to model the impact of pedestrian and bicycle accommodations on vehicular traffic performance.