Scoping Capacity

Several layers were examined as part of the highway improvement needs analysis conducted for the 2017 State Transportation Plan. Future capacity needs on the Primary Highway System were evaluated for the year 2040 with the Iowa Travel Analysis model (iTRAM). A volume-to-capacity (V/C) ratio was used, which divides the roadway’s forecast traffic by its capacity. A corridor is targeted to have a capacity need if the majority of its V/C values exceed 0.7, which is considered to be approaching capacity. Needs were identified at the corridor level; spot locations, generally defined as 0.5 miles in length, were not included as corridors. For more information, see iowadot.gov/iowainmotion.