20 CFR 404.1406: Eligibility to railroad retirement benefits as a bar to payment of social security benefits.

Notwithstanding the fact that, pursuant to the preceding provisions of this subpart, services rendered by an individual in the railroad industry are in employment, no lump-sum death payment or survivor monthly benefits shall be paid (except as provided in § 404.1407) under the regulations in this part on the basis of such individual's wages and self-employment income if any person, upon filing application therefor, would be entitled to an annuity under section 2 of the Railroad Retirement Act of 1974 or a lump-sum payment under section 6(b) of such Act with respect to the death of that individual; or for periods prior to 1975, would have been entitled to an annuity under section 5 or a lump-sum payment under section 5(f)(1) of the Railroad Retirement Act of 1937 with respect to the death of that individual.