List of Interstate Highways
There are 70 primary Interstate Highways in the Interstate Highway System, a network of controlled-access freeways in the United States. They are assigned one- or two-digit route numbers, whereas their associated "auxiliary" Interstate Highways receive three-digit route numbers. Typically, odd-numbered Interstates run south-north, with lower numbers in the west and higher numbers in the east; even-numbered Interstates run west-east, with lower numbers in the south and higher numbers in the north. Highways whose route numbers are divisible by "5" usually represent major coast-to-coast or border-to-border routes (ex. I-10 travels from Santa Monica, California, to Jacksonville, Florida, traveling from the Pacific to Atlantic oceans). Additionally, auxiliary highways have their numbering system where a different number prefixes the number of its parent highway.
Interstate 94 in Indiana
In Portage the interstate passes over US 20 and begins to parallel US 20, before having an interchange with SR 249. East of SR 249 the highway leaves Portage and enters Burns Harbor, before passing under SR 149. I-94 has a cloverleaf interchange with US 20, before entering Porter. While passing through Porter, the highway passes over a Norfolk Southern railroad track. After Porter the road enters Chesterton and has an interchange with SR 49. East of SR 49 the freeway leaves Chesterton entering rural Porter County, before entering LaPorte County. The interstate has an interchange with US 421 just south of Michigan City. The road curves to the northeast, bypassing Michigan City to the southeast, having an interchange with US 20. After US 20, I-94 passes over a Chicago South Shore and South Bend Railroad track, before leaving the Michigan City area and entering Michigan. The segment of freeway between US 20 and the Michigan state line has the lowest AADT on I-94 in the state of Indiana, at 37,179 vehicles.