There’s A Whole System Of US Highways That Many Don’t Know About

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As I continued my first trip for my Untold EV & Cleantech Stories project, I came across something I never thought I’d find: a whole system of highways I didn’t know about. Unlike the Interstate I was driving on, this set of highways has no pavement, but it has the potential to both relieve traffic from regular highways and reduce transportation-related pollution.

What I’m talking about is the US Marine Highway System, and it was the last thing I expected to see driving in Oklahoma and Arkansas along I-40. The first sign of it was when we crossed the Arkansas River near Webbers Falls. The sign read: “McClellan Kerr Arkansas River Navigation System – Marine Highway M40.”

I took this screenshot from Google Street View because taking pictures while driving is dangerous.

The idea of a marine highway so far from the ocean seemed unusual, but I had previously heard of people with house boats traveling the Great Loop route that surrounds the eastern United States, so the idea of marine traffic going so far inland wasn’t totally alien to me. To encounter something called a marine highway in Oklahoma was still a surprise, though. When we came across signage for the M-55 at the Mississippi River and the M-65 in Tennessee, we knew this was probably something worth looking up.

The US Department of Transportation has a special webpage all about this system of marine highways, complete with a map of the system:

Image by US DOT (Public Domain)

The system’s highways are numbered the same as nearby Interstate Highways that they could relieve congestion from if they were used more. The one I saw, M-40, would relieve congestion from I-40 if people moved more cargo along it instead of on the Interstate using trucks. The Mississippi River is designated M-55, to align with I-55.

There’s one big problem that the US DOT points out, though:

However, America’s waterways are underused. The benefits of using our marine waterways — such as reducing landside congestion and reducing system wear and tear — are not perceived on an individual level. Using our waterways more consistently would create more public benefits and incentivize shippers to use these critical transportation channels.

There’s a lot of extra capacity on this system going unused, and great benefits could occur if more companies shipped goods and material using river barges instead of strictly with trucks. Benefits include:

  • More jobs along the system
  • Less congestion on the interstates
  • Lower maintenance costs for interstates
  • Cleaner marine technologies would be funded faster
  • Cheaper shipping
  • Alternatives to the highways makes for more resiliency and redundancy
  • Ability to move larger amounts of materiel in the event of a major military conflict

I didn’t see a lot of congestion in Texas or Oklahoma outside of the cities, but nearly all of Tennessee’s section of I-40 was quite congested. People in the right lane would go 80-90 mph, and they were constantly getting stuck behind slower traffic that was either passing or simply camping in the left lane. Even removing 10% of truck traffic and putting that on barges instead would make a noticeable difference on eastern Interstate Highways.

How Do Cargo Ships Make It To Oklahoma?

If you look at a map of the Arkansas River, there are a number of reservoirs along the route, which means that there are dams on the river. Last time I checked, I couldn’t get even a small boat past a dam in New Mexico, so there’s not real way to get shipping containers up there.

Or is there?

It turns out that each dam along the Arkansas, as far up as Tulsa, Oklahoma, has a lock on the side. For those unfamiliar, a lock is a set of gates that allow boats to go up and down in elevation, and even follow waterways that go uphill. When the boat approaches, the first gate will be open, and the water between the gates will be at the lower (below the dam) water level. Once the boat is inside the lock, the rear gate shuts and the front one slowly opens or water is pumped in to gradually lift the boat to the higher water level. Once the levels are equalized, the boat can exit into the reservoir and then further upstream.

The dams are essential to marine traffic along these smaller rivers (compared to the Mississippi) because they allow the US Army Corp of Engineers to control the flow of water along the route. This way, the river almost never dries up or floods in ways that would keep the boats out.

Also, to be clear, large oceanic container ships don’t come up the Arkansas river or most others. Smaller tows of barges make the trip instead, with one boat dragging along a very large set of floating loads.

Barges in Tulsa, Oklahoma’s port.

Environmental Benefits

The biggest benefits to increased Marine Highway use are environmental.

First off, barge traffic is very quiet compared to highways. One could live right on the edge of the Arkansas River or most others and not hear anything as the barges, boats, and ships come by carrying huge loads. Each barge carries the same load as dozens of trucks, and a float of barges (a group of them all being pulled together) can relieve the need for hundreds of trucks. The noise level of a float of barges is quite small compared to hundreds of trucks going by.

Emissions per ton carried by water are about 1/8 those of loads carried by truck, and about half of those that would come from rail travel, even with fossil fuel boats. This alone could make a big impact.

There’s also a lot of potential for electrification in waterway shipping. Technologies are already in use elsewhere, allowing for a barge to carry its battery packs as cargo along with the other cargo. When they get to a port or charging area, the containers with battery packs inside can be removed, replaced with fresh packs by a crane, and then the barge continues down or up the river. The packs that get left behind can sit and slowly charge up waiting for the next boat that needs new power.

We certainly want to see more electrification in truck traffic, but the Marine Highway System provides alternatives that can both clean up transport today and allow for better electrification tomorrow.

Featured image by US DOT (Public Domain).

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Jennifer Sensiba

Jennifer Sensiba is a long time efficient vehicle enthusiast, writer, and photographer. She grew up around a transmission shop, and has been experimenting with vehicle efficiency since she was 16 and drove a Pontiac Fiero. She likes to get off the beaten path in her "Bolt EAV" and any other EVs she can get behind the wheel or handlebars of with her wife and kids. You can find her on Twitter here, Facebook here, and YouTube here.

Jennifer Sensiba has 1984 posts and counting. See all posts by Jennifer Sensiba