Most of you are probably aware of the Travel Model Improvement Program (TMIP) sponsored by the U.S. Department of Transportation, the Environmental Protection Agency, and the Department of Energy. This program is providing several tracks ranging from outreach through development of new algorithms.

We recently had the pleasure of attending the second TMIP conference in Daytona Beach, Florida. Items discussed included the TRANSIMS effort being conducted at Los Alamos Labs as well as many short term improvements. The conference was enlightening as well as inspirational. We are happy to see the interest in modeling and the interest in making it both more accurate and more precise.

TModel Corporation will continue to follow the progress and the information that comes from this effort. We are happy to see the emphasis placed on improvements such as feedback loops between the distribution and assignment process, refinement to better reflect speeds, time of day assignment and others. We were happy to hear the attention being paid to these concepts, because these have been important to us here at TModel Corporation for some time.

The modeling of intersection operation and delay has been a part of TMODEL software since 1982. The ability to model intersections has been enhanced over the years with dynamic turn penalties and the refinement of the Node Delay Coefficients (.NDC). Accurate (engineering type) speeds and capacities have also been important to us, with the Link Delay Coefficients (.LDC) having received a lot of attention to promote the modeling of realistic speeds. These speeds, of course, become much more important when dealing with Level of Service, Air Quality, and Fuel consumption issues.

The full featured distribution and assignment process has feedback built-in. In the incremental assignment process the distribution is recalculated for each increment of trips. By adjusting the distribution of each increment, you can better simulate the varying choices made by travelers as well as reflect the impact of congestion on destination choice. The efforts we are putting into the new TMODEL2 Distribution and Assignment module will enhance this capability as well as permit easy application for large models.

If you are interested in more information on TMIP, you may want to subscribe to the newsletter or contact the TMIP BBS. To find out more, contact Lynette Engelke, Texas Transportation Institute, 1600 E. Lamar Blvd., Ste. 112, Arlington TX 76011; FAX: 817-277-5439; e-mail: l- engelke@tamu.edu; bulletin board: (817) 277-7674.