49 CFR §211.51

1. (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. (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. (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. (3)The suspension is conditioned on the observance of standards sufficient to assure safety.
2. (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.
3. (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.