29 CFR 785.38 Travel that is all in the day's work.

Time spent by an employee in travel as part of his principal activity, such as travel from job site to job site during the workday, must be counted as hours worked. Where an employee is required to report at a meeting place to receive instructions or to perform other work there, or to pick up and to carry tools, the travel from the designated place to the work place is part of the day's work, and must be counted as hours worked regardless of contract, custom, or practice. If an employee normally finishes his work on the premises at 5 p.m. and is sent to another job which he finishes at 8 p.m. and is required to return to his employer's premises arriving at 9 p.m., all of the time is working time. However, if the employee goes home instead of returning to his employer's premises, the travel after 8 p.m. is home-to-work travel and is not hours worked. (Walling v. Mid-Continent Pipe Line Co., 143 F. 2d 308 (C. A. 10, 1944))