49 C.F.R. § 213.37 : Transportation — OTHER REGULATIONS RELATING TO TRANSPORTATION — FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION — TRACK SAFETY STANDARDS — ROADBED — Vegetation

Vegetation on railroad property which is on or immediately adjacent to roadbed shall be controlled so that it does not-

(a) Become a fire hazard to track-carrying structures;
(b) Obstruct visibility of railroad signs and signals:
(1) Along the right-of-way, and
(2) At highway-rail crossings; (This paragraph (b)(2) is applicable September 21, 1999.)
(c) Interfere with railroad employees performing normal trackside duties;
(d) Prevent proper functioning of signal and communication lines; or
(e) Prevent railroad employees from visually inspecting moving equipment from their normal duty stations.

49 C.F.R. §213.37