30 CFR § 57.9300 - Berms or guardrails.
(c) Berms may have openings to the extent necessary for roadway drainage.
(d) Where elevated roadways are infrequently traveled and used only by service or maintenance vehicles, berms or guardrails are not required when all of the following are met:
(1) Locked gates are installed at the entrance points to the roadway.
(2) Signs are posted warning that the roadway is not bermed.
(3) Delineators are installed along the perimeter of the elevated roadway so that, for both directions of travel, the reflective surfaces of at least three delineators along each elevated shoulder are always visible to the driver and spaced at intervals sufficient to indicate the edges and attitude of the roadway.
(4) A maximum speed limit is posted and observed for the elevated unbermed portions of the roadway. Factors to consider when establishing the maximum speed limit shall include the width, slope and alignment of the road, the type of equipment using the road, the road material, and any hazardous conditions which may exist.
(5) Road surface traction is not impaired by weather conditions, such as sleet and snow, unless corrective measures, such as the use of tire chains, plowing, or sanding, are taken to improve traction.
(e) This standard is not applicable to rail beds.
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