Piedmont Triad Regional Model (PTRM)

What is PTRM?

PTRM was developed cooperatively by United States Department of Transportation (USDOT), North Carolina Department of Transportation (NCDOT), Piedmont Authority for Regional Transportation (PART) and the four regional Metropolitan Planning Organizations (MPOs). PTRM 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 MPO. 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 PTRM area is made up of three full counties and parts of six additional counties. The planning area is constituted of 1,718 transportation analysis zones (TAZs) and four Metropolitan Planning Organizations. PART plays a model custodian’s role in 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 does PTRM work?

PTRM 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.

  • 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 route people will take

PTRM is developed on a transportation planning software platform, called TransCAD by the caliper, which is Geographic Information System (GIS) designed specifically for use by transportation professionals to store, display, manage, and analyze transportation data.

What does PTRM do?

PTRM analyzes socio-economic and travel characteristics data with the highway and transit network in the model area. Through the first two steps, PTRM predicts how many people travel to and from with various purposes on a daily basis within/beyond Triad region.

Through the last two steps, PTRM is performed to predict auto, transit and non-motorized travel demand (daily traffic volume, traffic volume by period) based on socio-economic data forecasts and level of service of the region’s road network and transit services at the model network consisting of roadways and transit routes for the future horizon years. The base year of PTRM version 3.2 is 2009 and three designated horizon years are 2015, 2025, and 2035. As of October in 2014, PTRM is being upgraded into version 4.0 with a new base year, 2013, and three new horizon years, 2021, 2030, and 2040 until 2015.

When the entire process is completed, PTRM 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 the Federal, the State and MPOs.