The Regional Travel Demand Model

PART manages the regional modeling program in partnership with the North Carolina Department of Transportation (NCDOT) Planning Department and the Greensboro, Winston-Salem, High Point, and Burlington-Graham MPOs. The program consists of four elements: the Regional Travel Demand Model (RTDM), the Advanced Freight Model (AFM), the Transit Boarding and Estimation Simulation Tool (TBEST) and CommunityViz Scenario Model (CVSM). The program is jointly funded by each agency listed above and saves each MPO approximately $100,000 a year through PART’s coordination of the program.

The Regional Travel Demand Model

RTDM was developed cooperatively by North Carolina Department of Transportation (NCDOT), Piedmont Authority for Regional Transportation (PART) and the four regional Metropolitan Planning Organizations (MPOs). RTDM is a multi-modal four-step regional travel demand model, designed to support long range transportation planning and programming decisions in the Triad region and in the Greensboro, Winston-Salem, High Point, and Burlington-Graham MPOs. More detailed analyses are Air quality conformity, Travel forecasts, Long range transportation plan development, Multimodal alternative analysis, Comprehensive transportation plan analysis, Regional analysis, and Framework for sub-area analysis.

The RTDM area is made up of four full counties and parts of five additional counties. The planning area is constituted of 1,932 transportation analysis zones (TAZs) and four Metropolitan Planning Organizations. As model custodian, PART’s custodial duty includes developing, maintaining and updating the model with the state of the practice to meet various needs from the federal, state, MPO and the private sector mainly including professional engineers.

How RTDM Works

RTDM utilizes a traditional four-step trip-based model process consisting of four basic steps below. Each step utilizes ‘state-of-the-practice’ and accepted mathematical models to objectively analyze why, where and how people travel. Steps:

• Trip Generation: to predict the number of trips to be made
• Trip Distribution: to predict where those trips go
• Mode Choice (Modal Split): to predict whether people take transit, their own car, or a carpool to and from work or another destination
• Traffic Assignment: to predict the number of traffic flow at highway and transit ridership by route and stop

What RTDM Does

RTDM analyzes socio-economic and travel characteristics data with the highway and transit network in the model area. Through the first two steps of the modeling process, RTDM predicts the number of people traveling to and from various places on a daily basis. These predictions take into account the purposes of travel and travel both within and beyond the Triad region.

During the last two steps the model process, predictions are made related to auto, transit and non-motorized travel demand (daily traffic volume, traffic volume by period) based on socio-economic data forecasts and the level of service of the region’s road network and transit systems. These predication are for the current "base" year and for 10-year increments or horizon years. When the entire process is completed, RTDM generates a report consisting of summarized performance measures such as speed, VMT by county and functional class of roadways. This report is utilized as main input data in the various transportation analyses for federal agencies, state agencies and MPOs.