In Downtown Garland, Highway 78 follows the central streets of Avenues B and D before joining Lavon Drive and moving northeastward.

For a month and a half, the traffic going between Wylie and the eastern portion of Collin County was diverted to go through the city of Rockwall, a nearly 20-mile (32 km) detour.

SH 78-D) is a 2.6-mile (4.2 km) long business route that runs through Blue Ridge in northern Texas.

SH 78-E) is a 2.4-mile (3.9 km) long business route that runs through Farmersville in northern Texas.

SH 78-F) is a 2.4-mile (3.9 km) long business route that runs through Copeville in northern Texas.

SH 78-G) is a 1.1-mile (1.8 km) long business route that runs through Lavon in northern Texas.