Section 4 of this Act provides that:
(a) Except as provided in paragraph (b), of this section, no
employer shall be subject to any liability or punishment under the Fair
Labor Standards Act of 1938, as amended, the Walsh-Healey Act, or the
Davis-Bacon Act, on account of the failure of such employer to pay an
employee minimum wages, or to pay an employee overtime compensation, for
or on account of any of the following activities of such employee
engaged in, on, or after May 14, 1947:
(1) 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, and
(2) Activities which are preliminary to or postliminary to said
principal activity or activities, which occur either prior to the time
on any particular workday at which such employee commences, or
subsequent to the time on any particular workday which he ceases, such
principal activity or activities.
(b) Notwithstanding the provisions of paragraph (a) of this section
which relieve an employer from liability and punishment with respect to
an activity the employer shall not be so relieved if such activity is
compensable by either:
(1) An express provision of a written or nonwritten contract in
effect, at the time of such activity, between such employee, his agent,
or collective-bargaining representative and his employer; or
(2) A custom or practice in effect, at the time of such activity, at
the establishment or other place where such employee is employed,
covering such activity, not inconsistent with a written or nonwritten
contract, in effect at the time of such activity, between such employee,
his agent, or collective-bargaining representative and his employer.
(c) For the purposes of paragraph (b) of this section, an activity
shall be
considered as compensable, under such contract provision or such custom
or practice only when it is engaged in during the portion of the day
with respect to which it is so made compensable.
(d) In the application of the minimum wage and overtime compensation
provisions of the Fair Labor Standards Act of 1938, as amended, of the
Walsh-Healey Act, or of the Davis-Bacon Act, in determining the time for
which an employer employs an employee with respect to walking, riding,
traveling, or other preliminary or postliminary activities described in
paragraph (a) of this section, there shall be counted all that time, but
only that time, during which the employee engages in any such activity
which is compensable within the meaning of paragraphs (b) and (c) of
this section.