Headings | Traffic on Primary Road System




Section length (miles) Annual average daily traffic

Vehicle classification distribution
of annual average daily traffic

Average daily vehicle miles


Cars, vans and pickups Total trucks and buses Single unit
All vehicles Trucks and buses
Primary route
section description




4 or more axles 4 or less axles


6 or more axles Multiple trailers



Route The official route numbers assigned to all Interstate, United States and Iowa routes in Iowa. Route sections that have two or more assigned primary route numbers are listed as follows.
Two interstate routes -interstate with lowest route number
Any interstate and primary route -with interstate route
Two U.S. routes -U.S. route with lowest number
U.S. and Iowa route -with U.S route
Two Iowa routes -Iowa route with lowest route number

Section description A general description of the route section. Special messages are not indented, general descriptions are indented two spaces. If the traffic volume has been estimated an asterisk(*) will be shown.
Rural/Municipal R = Rural       M = Municipal
Section length The length of the described highway section shown to the nearest 1000th of a mile.
Annual average daily traffic General unit of measure for traffic, which represents the annual average traffic per day (AADT). It is established by adjusting periodic counts to AADT by using factors derived from permanent continuous automatic traffic recorders.
Vehicle classification The distribution of vehicle types that could be expected on a typical day.
Average daily vehicle miles The product of the section length times the annual daily traffic. A separate average daily vehicle miles has been computed for trucks and buses. Pickups and vans are not considered trucks. Vehicle miles of curves, loops, connections and inner legs not considered on the traveled way are used to calculate the mainline vehicle miles and average daily traffic totals.
Iowa transportation background image