U.S. Highways in the state. The department tracks the traffic volumes along all state highways as a part of its maintenance responsibilities using a metric called average annual daily traffic (AADT). This measurement is a calculation of the traffic level along a segment of roadway for any average day of the year. In 2010, INDOT figured that the lowest traffic levels were 3,120 vehicles and 350 commercial vehicles used the highway daily near Ogden Dunes. The peak traffic volumes were 30,510 vehicles and 2,430 commercial vehicles AADT along the section of US 12 at the Illinois state line, concurrent with US 20 and US 41. The highway has been designated as the Iron Brigade Memorial Highway to honor the Civil War Union Army unit; it has the same designation in Michigan, Wisconsin and Illinois. Whiting to Gary US 12 enters Indiana concurrent with US 20 and US 41, at which point it passes under the Indiana Toll Road. The road passes both commercial and industrial areas between Wolf Lake and Horseshoe Casino. US 12, US 20, and US 41 are concurrent until US 41 turns south on Calumet Avenue. Both US 12 and US 20 head southeast toward East Chicago, where US 12 turns east while US 20 continues south. The route heads east through East Chicago as a four-lane undivided highway passing through mostly residential areas. The road heads south concurrent with State Road 912 (SR 912), passing through mainly industrial area between East Chicago and Gary. The two routes have an interchange at SR 312 and access to the Indiana Toll Road, via an interchange at Gary Avenue. The road has two bridges with the first passes over Grand Calumet River and the other passing over the Indiana Toll Road and the South Shore commuter rail line. After passing the rail line, the road has an interchange with US 20, this interchange is the southern end of the SR 912 concurrency. US 12 follows US 20 east towards downtown Gary, as a four-lane divided highway. The two highways pass through residential areas and crosses the Lake Shore and Michigan Southern Railway owned by Norfolk Southern Railway, before downtown Gary. At Bridge Street in Gary, the road becomes one-way streets, with westbound on Fourth Avenue and eastbound on Fifth Avenue. In downtown Gary it has an intersection with SR 53, locally known as Broadway. The streets also pass by