Interstate 345 overlays the southernmost section of U.S. 75 along the Central Expressway between Downtown and Cle Elum in Dallas. The route is unmarked, with U.S. 75 signed alone on the mostly elevated route between IH 30 / IH 45 and State Spur 366 (Woodall Rogers Freeway).
Exits along IH 345 extend the IH 45 numbering system northward to SS 366 (Woodall Rogers Freeway). They reset at the exchange with Woodall Rodgers Freeway, which is Exit 1 along U.S. 75 (Central Expressway) southbound.1
IH 345 was built in conjunction with the IH 45 / Central Expressway project in the 1970s.2 The designation was approved by AASHTO on June 30, 1970.