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need to be made whether or not the outcome is accept- able because either outcome, ultimately, will need to be supported by local decision makers. The second approach for testing the ABM will be directed at assessing the desire to develop a model that is more sensitive to policy variables. The policy- oriented tests will include evaluation of ⢠Outcomes in designated transit- oriented develop- ment areas; ⢠Effects of different regional development densities (e.g., single- family housing versus multi- family, and so forth); ⢠Development in known industrial areas; ⢠Development of specific âgreenfieldâ areas, to see how well the model can predict the spread of the urban area; and ⢠Outcomes in redevelopment areas. The policy- oriented tests will be even more subjective than the comparison of forecasts from the ABM and the traditional four- step model. To improve the usefulness of the tests, it will be important to reach a consensus regarding the expected outcome. If the outcome from the model does not match the expected outcome, the results will need to be assessed to determine whether they are illogical or providing valuable information that would modify the expected outcomes developed prior to run- ning the model. As discussed above, the definition of rea- sonableness may be derived from observed conditions in other cities. REFERENCES 1. Model Validation and Reasonableness Checking Manual. Travel Model Improvement Program, Federal Highway Administration, February 1997. 2. Bhat, C., and F. Koppelman. Travel Model Improvement Program e- mail, December 16, 2005. 3. Parsons Corporation and Cambridge Systematics, Inc. âValidation Plan for the DRCOG Activity- Based Model.â March 2006. 156 INNOVATIONS IN TRAVEL DEMAND MODELING, VOLUME 2