The Tennessee state routes do not follow a systematic numbering system unlike the U.S. Highway System and some other states' highway systems. The routes are separated into primary and secondary routes though. Many of the routes are hidden in that they are overlaid on U.S. Routes and not signed. The mile markers throughout Tennessee, however, show the state route number for these hidden routes.

Primary and secondary state routes
All Tennessee Primary State Routes in black with Interstates in blue
System information
Maintained by TDOT
Highway names
Interstates	Interstate XX (I-XX)
US Highways	U.S. Route XX (US XX)
State	State Route XX (SR XX)
System links
Tennessee State Routes Interstate US State

The Tennessee Department of Transportation (TDOT) maintains these routes under the "State Highways" title of state law,^[1] but designates them as "state routes". The triangle marker design was the only design until November 1983, when Tennessee divided its routes into primary routes and secondary or "arterial" routes with the adoption of a functional classification system, creating a primary marker and making the triangle marker the secondary marker; primary marker signs were posted in 1984.^[2]