US DOT Marine Highway Corridors

[kurumi]

http://www.marad.dot.gov/ships_shipping_landing_page/mhi_home/mhi_home.htm

"These all-water routes consist of 11 Corridors, 4 Connectors and 3 Crossings that can serve as extensions of the surface transportation system.  These corridors identify routes where water transportation presents an opportunity to offer relief to landside corridors that suffer from traffic congestion, excessive air emissions or other environmental concerns and other challenges."

There's a map at the above link. Marine highways include:

M-A1 (Alaska)
M-2 (Puerto Rico)
M-5, M-84, M-580 (West coast)
M-10, M-49, M-40, M-55, M-65, M-70 (Miss. River and Gulf)
M-90, M-75, M-71/77 (Great Lakes) - M-90 has three parts
M-95, M-64, M-87 (East coast)

All intersections will likely be at grade.

[TheStranger]

Interesting that it's M-580 and not M-80 for the Bay Area route...I would think that the Marin-Oakland corridor isn't quite as busy as the SF-Oakland corridor, though I know both routes have ferries.

US 9 and US 10 represent actual signed routes on ferries...would this concept be similar?

[Bickendan]

The map suggests M-580 heads to Sacramento, so is the number suggestive of a combination of I-5 and I-80 as opposed to say I-580?

Note that the spur to Portland is M-84, though. M-80 might've made more sense. Also, M-84 should technically go all the way to the Tri-Cities...

I do like that M-5 seems to be I-5's counterpart... and goes all the way to essentially Anchorage.

[WillWeaverRVA]

M-95 is the same way. In fact, all the marine highways are numbered after a nearby interstate highway. The only exception is M-2, which has no equivalent, although it would fit in the grid if one of the Puerto Rico interstates somehow became I-2 instead.

[Bickendan]

Well, technically...

[oscar]

When Alaska applied in 1960 for Interstates of its own, one of its proposed routes was the Alaska Marine Highway System mainline through SE Alaska's "Inside Passage."  The Bureau of Public Roads (FHWA's predecessor) blew off this suggestion, apparently couldn't get behind the concept of a liquid Interstate.'

However, that and other ferry routes did get designations as Federal Aid Primary highways.  I think the mainline Inside Passage route was FAP 95.

[WillWeaverRVA]

Well, technically...

I saw that, but the spur route in Alaska is M-A1. The route in Puerto Rico is simply M-2.

[NE2]

Interesting that it's M-580 and not M-80 for the Bay Area route...I would think that the Marin-Oakland corridor isn't quite as busy as the SF-Oakland corridor, though I know both routes have ferries.

US 9 and US 10 represent actual signed routes on ferries...would this concept be similar?

No. This is almost certainly primarily for freight. 580 is still a strange number, however.

[andytom]

Note that the spur to Portland is M-84, though. ... Also, M-84 should technically go all the way to the Tri-Cities...

It does.  From the accompanying description documentation it actually goes all the way up the Columbia River and Snake River to Lewiston, ID.

--Andy