The Maine Port Authority and a tugboat company have developed a design for a hybrid vessel that could carry shipping containers between Portland and New York City – and revive a coastal domestic shipping system that disappeared more than a half-century ago.

Officials with the port authority and McAllister Towing and Transportation hope the innovative tug-barge design and a newly completed business plan will spur the federal government to support the project as a way to get trucks off the Northeast’s congested highways.

The idea is to create a public and private partnership to both build the vessel and operate the service. The vessel’s construction cost is estimated to be as high as $75 million, according to a study released Tuesday.

That’s a third of the cost of a comparable ship, and the operating costs also would be less because a barge would require a much smaller crew, said John Henshaw, executive director of the Maine Port Authority.

“The $75 million seems like a high number, but when you compare it to a ship, it seems like a good deal,” he said.

Moving heavy trucks off the nation’s crowded highways has been a priority for the Obama administration. Paul “Chip” Jaenichen, the top official in the U.S. Maritime Administration, said the administration is committed to developing a transportation system that can provide additional capacity to accommodate growing freight volumes.

“Innovative transportation projects, like this vessel, move us closer towards that reality,” he said in an email.

Coastal domestic shipping was the primary way to move cargo between cities along the East Coast before the construction of the interstate highway system after World War II put the steamship lines out of business, said Jack Humeniuk, business agent for the longshoremen’s union in Portland.

The last barge service between New York and Portland, which ended in 2009, was a feeder service for containers that were transferred to huge freighters for delivery overseas.

The new service would be geared for the domestic market, allowing Maine shippers to transport their containers to the Red Hook Container Terminal in Brooklyn. From there, the containers could be placed on trucks going to customers within the New York metropolitan area, a market with more than 20 million people.

Shippers abandoned the previous service because it often ran into delays in the winter when the tug, which towed the barge, couldn’t handle rough seas.

In the proposed design, the tug would attach directly to the barge while pushing it, giving it much greater control over the barge, said Charles Cumming, an official with McAllister, which is based in New York City and also owns Portland Tugboat.

“When the tug is locked into place, the whole unit acts like a ship does,” he said.

He said the tug could be disengaged to allow it to push a different barge.

The idea of a modular tug-barge combination is not new. For years, similar vessels have moved refined petroleum products and in some cases bulk cargo, such as coal. But this vessel would carry shipping containers, making it the first such vessel in the nation and likely the world, Cumming said.

He said the barge would have slots allowing crane operators to easily stack containers and on-board generators would allow them to be refrigerated.

The barge would make once-weekly round trips between Portland and New York City, taking 24 hours each way, according to the study.

The service also would stop at a yet-to-be identified port in southern New England. Eventually, similar domestic shipping services could be created elsewhere along the eastern seaboard, Henshaw said.

“If this service works, you should be able to replicate the model down the coast,” he said.

Heavy, low-priced commodities and products would be ideal cargo for the service because it costs less to move heavy cargo by water and the speed of delivery is not as critical, according to the market analysis.

The potential cargo identified in the study included potatoes, processed frozen lobster, processed frozen fish, wood pulp, saw logs, newspaper, paper rolls, bottled alcoholic and nonalcoholic beverages, bottled water and dry grocery goods.

The study assumes many of the containers would be empty on the return trip to Portland.

Improvements in transportation would make Maine companies more competitive and open up new markets, said John Williams, president of the Maine Pulp and Paper Association.

“Anything that can be done to make transportation faster or more reliable or less expensive would be a real advantage,” he said.

Larus Isfeld, general manager for Eimskip USA, an Icelandic container line that connects Portland with northern Europe, said barge service would allow shippers in New York to transport products to Portland and then to the niche markets that Eimskip serves: Norway, Iceland, Greenland and the Faroe Islands. In turn, products from those countries, such as bottled water from Iceland, could be shipped on the barge to the New York market.

Besides opening up new markets, the increase in volume of containers moving through the International Marine Terminal in Portland would make the port more efficient and competitive, Isfeld said.

The design and market study was funded through a $150,000 grant from the U.S. Maritime Administration.

The next step, Henshaw said, is to get the potential partners – including McAlister, the Red Hook Container Terminal, the Port Authority of New York & New Jersey, another so-far unidentified port in southern New England, and Maine’s congressional delegation – to put together a plan to get the project funded with both private and public money.

The route between Portland and New York City has been identified by the federal government as a part of the nation’s “marine highway” system. It even has a name, M95, to serve as the waterborne counterpart of I-95, the highway that parallels the route.

Since 2009, the Obama administration has awarded more than $100 million in Transportation Investment Generating Economic Recovery – or “TIGER”– grants to projects that increase the usage of the marine highways. In addition, the U.S. Maritime Administration also has awarded $6.3 million for marine transportation-related infrastructure and equipment through its Marine Highway Grant program.