(a) Classes of service covered. Conditions under which remuneration with respect to a day may not be payable to or accrue to an employee solely because of the application to him of a mileage or work restriction exist in train-and-engine service, yard service, dining-car service, sleeping-car service, and other Pullman-car service, and similar service, and express service on trains. In the determination of a claim for benefits of an employee in any other service, the employee's lack of remuneration with respect to any claimed day shall be presumed not to be due solely to the application of a mileage or work restriction. Conditions under which remuneration with respect to a day may not be payable to or accrue to an employee solely because he is standing by for or laying over between regularly assigned trips or tours of duty exist in train-and-engine service, dining-car service, sleeping-car service, and other Pullman-car service, and similar service, and express service on trains. In the determination of a claim for benefits of an employee in any other service, the employee's lack of remuneration with respect to any claimed day shall be presumed not to be due solely to his standing by for or laying over between regularly assigned trips or tours of duty.

(b) Sickness claims. An employee who, in connection with a claim to a day as a day of sickness, is held to be not able to work because of any physical, mental, psychological, or nervous injury, illness, sickness, or disease shall not be considered to lack remuneration with respect to such day solely because of the application to him of mileage or work restrictions or solely because he is standing by for or laying over between regularly assigned trips or tours of duty. Nor shall a female employee be considered to lack remuneration with respect to a day solely because of the application to her of mileage or work restrictions or solely because she is standing by for or laying over between regularly assigned trips or tours of duty if the day is one on which, because of pregnancy, miscarriage, or the birth of a child,