46 C.F.R. § 136.230 – Routes permitted.

(a) The area of operation for each towing vessel and any necessary operational limits are determined by the cognizant OCMI and recorded on the vessel's COI. Each area of operation, referred to as a route, is described on the COI under the major headings “Oceans,” “Coastwise,” “Limited Coastwise,” “Great Lakes,” “Lakes, Bays, and Sounds,” or “Rivers,” as applicable. Additional limitations imposed or extensions granted are described by reference to bodies of waters, geographical points, distances from geographical points, distances from land, depths of channel, seasonal limitations, and similar factors.
(b) Operation of a towing vessel on a route of lesser severity than those specifically described or designated on the COI is permitted, unless the route is expressly prohibited on the COI. The general order of decreasing severity of routes is: Oceans; coastwise; limited coastwise; Great Lakes; lakes, bays, and sounds; and rivers. The cognizant OCMI may prohibit a vessel from operating on a route of lesser severity than the primary route on which a vessel is authorized to operate, if local conditions necessitate such a restriction.
(c) When designating a permitted route or imposing any operational limits on a towing vessel, the cognizant OCMI may consider:
1. (1) The route-specific requirements of this subchapter;
2. (2) The performance capabilities of the vessel based on design, scantlings, stability, subdivision, propulsion, speed, operating modes, maneuverability, and other characteristics;
3. (3) The suitability of the vessel for nighttime operations and use in all weather conditions;
4. (4) Vessel operations in globally remote areas or severe environments not covered by this subchapter. Such areas may include, but are not limited to, polar regions, remote islands, areas of extreme weather, or other remote areas where timely emergency assistance cannot be anticipated; and
5. (5) The TSMS applicable to the vessel, if the vessel has one.