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32 Link-by-link comparisons (1) Network flows to match counts by mode of transportation, Other (1) with emphasis on interurban routes. Match increments of land to changes in land price. Match CTPP distribution for commuting flows. Only nine states reported using the Model Validation and Reasonableness Checking Manual (BartonAschman Asso- Each criterion has a specific numeric target. The network flows, ciates, Inc. and Cambridge Systematics, Inc. 1997). for example, must fall within specified ranges based on total ob- served volume. Some targets are more liberal than for traditional urban travel models, owing to the complexity of the integrated Most states did not provide a qualitative assessment of how models and their coarser geographic detail. well their models validated. A few states gave vague responses, such as "well," "acceptable," and "fair." Texas reported good Several subjective performance tests were also developed. Each comparisons between its freight component and flows from required the model to produce sensible and reasonable results. Reebie's database. California stated that 44% of the links meet Additional criteria for which specific numeric targets could not the "maximum desirable deviation" standard and an R-square be defined include: of 0.83 between link counts and base case link volumes. Michi- gan reported that 80% of links in major corridors were within Destination and route choice response behavior. Trip generation sensitivities. the "standard." Louisiana provided a "maximum desirable de- Path and transportation cost testing. viation" chart showing 95% of links meeting the standard. Only two states used OD table estimation from traffic counts, which would tend to arbitrarily improve the match between observed POST-PROCESSING and forecasted volumes before validation. Post-processing of model results is sometimes needed to ob- Because of the larger scales of statewide models, there is tain information that is compatible with decision processes an expectation that the accuracy of these models would be on alternatives or policies. The need for post-processors de- less than urban models. Approximately half of the states ap- pends on the already built-in capabilities of the state's travel plied the same validation standards to statewide models as forecasting software package. States reported some post-pro- urban models. The other half used less stringent standards for cessing for air pollution emissions, benefits evaluation, level their statewide models. Louisiana explained that because of service determination, and economic impacts. most of their links in the statewide model were low volume, it was possible to meet the looser criteria for urban roads of Air pollution emissions (9) similar volumes. Level of service determination (7) Benefitcost analysis (3) Oregon's model, having an unusual structure, also had un- Economic impact (2) usual validation criteria. Factoring volume-to-capacity ratios (1) Validation and model performance statistics (1) Research of current practices surprisingly found no existing clearly defined model calibration or validation criteria for inte- Indiana and Michigan use the same post-processor for grated land usetransportation modeling. The modeling team economic impact, which is a commercial regional economic and Peer Review Panel together developed several criteria for analysis package. Indiana assesses project benefits with assessing model performance for the Gen1 Model: Highway Economic Requirements System and in-house soft- ware, whereas Michigan uses a benefits module developed Match production by sector and zone. by a local university. Virginia reported the need to adjust Match number of trips and average trip distances by trip purpose. volume-to-capacity ratios downward to account for the un- Minimize zone-specific constants by sector. usually sparse networks with urban areas.