Business routes of Interstate 45

All of the business loops are maintained by the Texas Department of Transportation (TxDOT). Interstate 45 (I-45) has four business loops in the state, all located in northern Texas. Along I-45, TxDOT identifies each business route as Business Interstate 45 followed by an alphabetic suffix. Along Texas Interstates, the alphabetic suffixes on business route names ascend eastward and northward. There are gaps in the alphabetic values to allow for future system expansion. The alphabetic naming suffixes are included as small letters on the bottom of route shields.

I-45 business routes generally follow the path of the former U.S. Highway 75 (US 75) through the central portions of towns now bypassed by the Interstate route.