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Jennifer Wiltgen <br />Minnesota Department of Transportation <br />Figure 3: Model Performance for Segments with Counts <br />200 <br />Percentage Difference <br />150 <br />100 <br />50 <br />• •• • • <br />• <br />• <br />• 0• <br />v. • • • <br />• • • -•_ •• <br />• <br />s • /*-� {� �-y <br />• 1 11 11 1 l L lfll !1 1fl • l ii <br />-50 <br />-100 <br />rilli"I <br />Count <br />200000 <br />June 25, 2021 <br />Page 6 <br />Model Traffic Volume Adjustment Process <br />The final step in model development was to establish a process for adjusting the future modeled <br />volumes to account for the error in the base model. The National Cooperative Highway Research <br />Program Special Report 255 suggests methods of adjusting models based on: a) the difference between <br />model and count; b) the ratio of the model to county; and c) the magnitude of growth between existing <br />and future. The calculations used in this process are provided below: <br />• Ratio Method: AdjustedVolume Volume = FutureModel Volume x BaseCount <br />BaseModelVolume <br />• Difference Method: AdjustedVolurne = FutureModelVolume + (BaseCount — BaseModelVolume) <br />• Average Method: Average of Ratio Method and Deerence Method <br />