Known locally as Fredericksburg Road, it is a major arterial for the cities of San Antonio and Balcones Heights, providing access to the headquarters of United Services Automobile Association (USAA) and to the South Texas Medical Center.

Spur 345 follows Fredericksburg Road from the southern city limits of Balcones Heights.

It continues north through the South Texas Medical Center, crossing Wurzbach Road (which becomes Wurzbach Parkway further east), before ending at I-10/US 87 (McDermott Freeway) on the northwest side of the city.

[4] On January 26, 1962, when US 87 was rerouted onto the I-10 freeway to the east, the section of Fredericksburg Road was kept on the state highway system as Loop 345.

[5] On December 18, 2014, the section from I-410 south to I-10 was removed from the state highway system, while the remaining segment was redesignated Spur 345 as part of TxDOT's San Antonio turnback program, which returned 21.8 miles (35.1 km) of roadways to the city.