I-470 is one of 13 auxiliary Interstate Highways in Ohio and the only auxiliary Interstate Highway in West Virginia. The Ohio Department of Transportation and West Virginia Division of Highways (ODOT and WVDOH) conduct surveys on their highways to measure traffic volume. This is expressed in terms of average annual daily traffic (AADT), a measure of average traffic volume for any day of the year. In 2012, they calculated that 26,500 vehicles traveled along the highway at the eastern terminus in West Virginia, and 37,840 vehicles used I-470 across the Vietnam Veterans Memorial Bridge. As part of the Interstate Highway System, the entire route is listed on the National Highway System—a system of roads that are important to the nation's economy, defense and mobility.