Thurston Regional Planning Council (TRPC) obtained TMODEL2 in 1989 with the intent of using it for regional and local planning and traffic analysis. At the time, TRPC had only one staff person experienced with traffic modelling, and that experience was not with TMODEL2. Reports from other users that TMODEL2 was easy to learn and well supported were critical to our selection of the software.

TMODEL2 did turn out to be relatively easy to learn. The hard part about creating a model from scratch lies not with using the software, but with obtaining satisfactory input data in a timely manner. A traffic model requires voluminous input data, including population and employment data for each traffic analysis zone; speed, capacity, and number of lanes for each link in the network; and intersection characteristics for network nodes. After the model is assembled, traffic count data are required at numerous locations to help calibrate the model. Obtaining such data and reaching consensus on its accuracy becomes an even bigger task when different departments and jurisdictions are involved, as is typical in regional planning.

TRPC staff have handled several of the key data chores by working with our Technical Advisory Committee (TAC), which includes planning and public works staff from WSDOT and Intercity Transit. The TAC has helped obtain network and count data from each jurisdiction so a consistent regional network can be assembled. During that process, the TAC agreed on a quick method for simple capacity estimates. The TAC is now helping review population and employment estimates and forecasts. But in spite of the TAC's valuable assistance, data chores have been very time consuming.

So far, assembling our regional traffic model has taken more than a year, and calibration is not yet complete. Population and employment data have been by far the most time consuming part of the job. One interesting wrinkle developed when we learned that two of our cities were working with a consultant to use TMODEL2 for local traffic studies. TRPC entered into an agreement with the consultant so he could use some of our regional data in exchange for teaching TRPC staff some tricks of the trade.

In the near future TRPC intends to finish calibrating the model and start using it to help analyze transportation alternatives. The model will be a key tool in developing the new regional transportation plan required by the 1990 growth management act.