29 CFR 785.34 - Effect of section 4 of the Portal-to-Portal Act.
The Portal Act provides in section 4(a) that except as provided in subsection (b) no employer shall be liable for the failure to pay the minimum wage or overtime compensation for time spent in “walking, riding, or traveling to and from the actual place of performance of the principal activity or activities which such employee is employed to perform either prior to the time on any particular workday at which such employee commences, or subsequent to the time on any particular workday at which he ceases, such principal activity or activities.” Section 4(a) further provides that the use of an employer's vehicle for travel by an employee and activities that are incidental to the use of such vehicle for commuting are not considered principal activities when the use of such vehicle is within the normal commuting area for the employer's business or establishment and is subject to an agreement on the part of the employer and the employee or the representative of such employee. Subsection (b) provides that the employer shall not be relieved from liability if the activity is compensable by express contract or by custom or practice not inconsistent with an express contract. Thus traveltime at the commencement or cessation of the workday which was originally considered as working time under the Fair Labor Standards Act (such as underground travel in mines or walking from time clock to work-bench) need not be counted as working time unless it is compensable by contract, custom or practice. If compensable by express contract or by custom or practice not inconsistent with an express contract, such traveltime must be counted in computing hours worked. However, ordinary travel from home to work (see § 785.35) need not be counted as hours worked even if the employer agrees to pay for it. (See Tennessee Coal, Iron & RR. Co. v. Musecoda Local, 321 U.S. 590 (1946); Anderson v. Mt. Clemens Pottery Co., 328 U.S. 690 (1946); Walling v. Anaconda Copper Mining Co., 66 F. Supp. 913 (D. Mont. (1946).)