49 C.F.R. § 211.51

(a) Pursuant to the Department of Transportation Act (80 Stat. 931, 49 U.S.C. 1651 et seq.), the Federal Railroad Safety Act of 1970 (84 Stat. 971, 45 U.S.C. 421, 431-441), or both, the Administrator may temporarily suspend compliance with a substantive rule of the Federal Railroad Administration, if:

(1) The suspension is necessary to the conduct of a Federal Railroad Administration approved test program designed to evaluate the effectiveness of new technology or operational approaches or instituted in furtherance of a present or proposed rulemaking proceeding;

(2) The suspension is limited in scope and application to such relief as may be necessary to facilitate the conduct of the test program; and

(3) The suspension is conditioned on the observance of standards sufficient to assure safety.

(b) When required by statute, a notice is published in the Federal Register, an opportunity is provided for public comment, and a hearing is held in accordance with § 211.25, before the FRA approved test program is implemented.

(c) When the Administrator approves suspension of compliance with any rule in connection with a test program, a description of the test program containing an explanatory statement responsive to paragraph (a) of this section is published in the Federal Register.