To simplify, streamline and standardize the travel demand modeling process we propose to develop guidelines for best practices for developing travel demand models and sub-models for trip generation, distribution, mode choice and assignment. In addition, we will develop recommendations for sources of relevant data, i.e., socioeconomic data, and we will undertake various kinds of validations of forecasts. These products and associated tools will help assure that NCDOT staff members efficiently use their time and resources to carry out their statewide transportation planning and modeling mission.
The study will last three fiscal years will have two phases of approximately 1.5 years each. In Phase I, instead of using the same expensive transportation, air quality and impact and analysis approach for all communities, we propose developing appropriately scaled approaches that reduce time and cost, yet provide adequate estimates of traffic volumes and impacts resulting from new transportation projects. For example, conventional NCDOT trend line traffic forecasts are adequate for isolated highway projects in very small communities and rural areas. In towns with populations between 1,000 and 5,000, traffic forecasts and manual allocation methods are appropriate. As the size of the study area grows, quick response software is valuable. Our research will determine what thresholds might be appropriate for quick-response methods. Such software often uses national averages for travel demand model parameters and significant data collection savings accrue. The research team will adjust national averages to North Carolina values as necessary based on analysis of North Carolina travel data. We will focus on the quick response methodology used in TransCAD, as NCDOT is already heavily invested in TransCAD. Phase II will deal with guidelines and tools for larger areas. As the study area becomes larger including one or more MPO's or RPO's with multiple modes, TransCAD software will be the recommended tool following current NCDOT practice. However, we anticipate that efficiencies are possible through standardized GDSK sub-models and GIS displays.
We propose a flexible multi-phase, multi-year research program that captures the expertise of NCDOT, the TRM Service Bureau, and the two Universities. Besides producing specific guidelines for using alternate travel demand model approaches depending on community size and/or needs, we will identify and develop sub-models and tools for carrying out travel demand model analysis.
