- The busiest spot on Iowa's roadways is on I-235 in Des Moines between 56th Street and 42nd Street where the average daily traffic in 2015 was 130,800 vehicles per day.
Traffic counts by county or city
- Motor vehicles on Iowa's public roads traveled an estimated 33.13 billion miles in 2015.
- The Primary Road System, which is managed by the Iowa DOT, represents 63.0 percent of the total road mileage in the state. However, these roads carry 62.8 percent of all vehicular traffic. (2015)
- The weighted average daily traffic count on Iowa's Interstate Highway System is 21,910 vehicles in rural areas and 42,689 in municipal areas. (2015)
- The weighted average daily traffic count on rural county roads is 163 vehicles. The weighted average on municipal streets is 1,311 vehicles. (2015)