This report summarizes traffic operational evaluation of six select traffic impact analysis (TIA) case sites and the effectiveness of forecasting methods used in TIA studies. Six TIA case sites comprising 15 signalized intersections and 2 unsignalized intersections in North Carolina (four sites in the Charlotte region and two sites in the Raleigh region) were considered for comparison. Data collected during morning peak hours (7 AM - 9 AM) and evening peak hours (4 PM - 6 PM) on a typical weekday were used for evaluation. The measures of effectiveness (MOEs) considered for the evaluation of data are total number of hourly stops, 50thpercentile queue length, average intersection delay, and level-of-service (LOS). The comparison of operational performance and forecasting methods was conducted using three different methods. The first method was used to compare the operational performance at selected intersections before and after the construction of the new development proposed in the TIA study using Synchro® traffic simulation software. The second method was used to compare ""what was forecasted to happen after the development?"" with ""what is happening after the development?"" using Synchro® traffic simulation software. The third method was used to compare outcomes obtained using Synchro® traffic simulation software with field observations after the development.
Results obtained from the evaluations indicate that new developments naturally have a considerable effect on operational performance at intersections near the development. The build-out year forecasted traffic volumes and traffic conditions had not been reached for the six reviewed TIA reports. This difference can at least in part be attributed to economic conditions and the fact that several of the site’s still had vacant parcels / outlots and additional unconstructed development. Recognizing that seasonal traffic fluctuations can have a significant impact on the magnitude of commercial site traffic, improved forecasts and traffic operational condition modeling could be achieved with improved regional traffic growth rates, conservative peak hour factors (PHF) and use of representative heavy vehicle percentages. Given the variability and significance of the build out of complex mixed use sites a five year build out horizon may be more appropriate for determination of needed improvements and acceptable.
