For several years, Portland Metro's Transportation Research and Modeling Services division (TRMS) has been developing dynamic traffic assignment (DTA) tools for use in medium- and long-range regional transportation planning efforts. Technical obstacles have been overcome and crucial staff experience and expertise have been gained. Now, with the availability of DTA as an exciting new tool available for use by the planning community, another challenge presents itself: How does one get the transportation planners and decision makers to accept and implement this valuable asset?

The advantages of DTA over traditional static assignments are clear: DTA provides a temporal dimension to traffic assignment that is necessary to answer questions about the location, duration, and impact of congestion on the transportation network, and how this changes day-to-day, corridor-to-corridor. This allows the analyst and decision makers to gain a better understanding of complicated notions of travel time reliability, congestion management strategies, and air quality and emissions impacts at large sub-regional or regional scales.

Yet, very few public agencies have utilized DTA for medium- and long-range planning purposes. Most DTA project applications have been limited to near-term operational studies. Part of this is due to technological and methodological issues--DTA requires more rigor than traditional static assignment models in terms of model inputs and network development--and part of this results from a natural hesitation to readily adopt new, state-of-the-art tools until they've been proven effective on other similar projects.

Overcoming the hesitation of planners to utilize an 'unknown' tool for longer-range planning is the next challenge facing transportation modelers. This presentation focuses on the attempt to breakdown this barrier in Portland through the following methods:

• Actively promoting the benefits of DTA and how this new tool can provide answers to important policy questions that until now have been impossible to ascertain

• Identifying and developing the types of measures of effectiveness on our clients' wish lists to demonstrate the usefulness of DTA

• Focusing on specific demonstration long-range projects, often in parallel with on-going planning analyses, to demonstrate the additional evaluation measures DTA can provide that may influence the project alternative selection process