Introduction - The Complexity of the Transportation Planning Environment

The current multimodal transportation planning environment is one in which financial constraints require transportation planners to consider a variety of proposed improvements. The challenge for decision makers is to determine which alternatives are effective and financially feasible. The alternatives to be considered may include policies, plans, projects and programs designed to improve mobility, accessibility and the environment. Evaluating alternatives designed to ensure the efficient use of both the existing and future transportation systems often places additional pressure on planners to provide decision makers with objective data and analysis. Quantifying future transportation system performance and identifying potential operational deficiencies can benefit the decision making process. An effective means of quantifying demand and assessing the performance of alternative options is to develop and maintain a set of travel demand models.

Travel Demand Models - An Effective Planning Tool

Travel demand models are an invaluable tool that provides metropolitan planning organizations (MPOs), ADOT, and other planning partners with several potential uses and benefits including the ability to:

• Provide technical analyses supporting plan and policy development
• Project anticipated future outcomes for public involvement meetings
• Evaluate proposed transportation improvement projects and programs
• Identify transportation system deficiencies
• Evaluate transportation improvement options and development scenarios
• Conduct traffic, corridor and sub-area studies
• Support air quality and energy analyses
• Conduct freight and goods movement studies

Informed Decisions Enabled By Travel Demand Models

Travel demand models enable informed decision making on transportation improvement options. Such informed decision making often rests on the ability to evaluate proposed improvements. Travel demand models serve that purpose by offering a wealth of information identifying transportation system deficiencies and assessing the performance of the various alternatives, including:

• Existing and future traffic on highway facilities and ridership on transit services
• Congestion and crowding on existing and proposed highways and transit systems
• Point-to-point travel times and distances
• Changes in average trip distances and travel time by trip purpose and by time of day
• Number of trips to major activity centers
• Vehicle miles and hours of travel
• Future travel demand within a corridor
• Market analysis – winners and losers

Travel Demand Models - Supporting Design Level Traffic Forecasts

Another important application of travel demand models is supporting the development of engineering design and traffic operations forecasts. The ADOT Multimodal Planning Division develops travel forecasts to support future design-level traffic estimates for the engineering of proposed projects. Estimates of future traffic volumes based on the travel demand models are used to support operational considerations such as roadway lane configurations, traffic signal timing, pavement design, traffic weaving analysis and placement of access/egress facilities.

Developing Travel Demand Models - A Cooperative Process with Local & Regional Organizations

The development of travel demand modeling capability is a cooperative process between local agencies, MPOs and ADOT. Local agencies and MPOs collect much of the data used in the development and calibration of travel demand models. MPOs develop and validate the travel models either independently or with ADOT assistance. ADOT provides technical guidance and collaborate as required to compile the information needed for model development. ADOT stands ready to help with modeling requirements including: base year and future year demographic data; regional roadway inventory data; and, the software platform for travel demand modeling. Once the travel models are validated, the ADOT Multimodal Planning Division offers additional assistance for loading software/files, displaying networks, developing alternatives and performing various system performance analyses. This affords local planners the opportunity to fully utilize the regional travel demand models in support of long-range planning, TIP development, major investment studies, and transportation system operations.