All of the business loops within Texas are maintained by the Texas Department of Transportation (TxDOT). Interstate 20 (I-20) has 15 business loops in the state, all located in western Texas. Along I-20, TxDOT identifies each business route as Business Interstate 20 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.