Drivers nationwide could find themselves sharing the roads with longer double-trailer trucks under a proposal making its way through Congress.

Large trucking companies and a national industry group are urging lawmakers to allow longer trailers, arguing that doing so would increase efficiency and move more goods with fewer trucks.

Republicans in both chambers of Congress strongly support the truckers’ effort, but it has sparked outrage among safety advocates.

Double trailers could stretch to 33 feet instead of the current 28 feet under a provision in a transportation spending package awaiting consideration by the full Senate. The House has passed a spending bill that also includes the provision.

The trailer debate comes as forecasters see major increases on the nation’s transportation network in the coming decades — with few signs of a dramatic increase in infrastructure spending or major change in the way the country moves goods.

“Are there opportunities to reduce congestion and move goods more efficiently in a more cost-effective way?” asked Rep. Frank A. LoBiondo, a New Jersey Republican who ran a trucking business before coming to Washington. “I think that’s what we’re going to have to debate.”

Highway safety advocates don’t see truck length as an efficiency issue. They’re calling for Congress to apply the brakes, saying safety questions are still unanswered.

“What we’re talking about is people’s lives,” said Joan Claybrook, chairwoman of Citizens for Reliable and Safe Highways. “It’s not just an economic issue. This is a life and death issue.”

Big Shippers Push

Big U.S. shipping companies signaled they’d be jumping into the ring early to fight for longer trucks.

FedEx, UPS, Con-Way, Estes Express Lines and other major shippers formed the Coalition for Efficient and Responsible Trucking and said in February they wanted to insert a trailer- extension provision into the next highway bill.

The group’s pitch is simple: Trucks fill up before they hit the weight limit, wasting space, time and resources. Longer trucks are fuller trucks, but the group doesn’t need any increase in the federal weight limit.

“Everyone — Republicans and Democrats — is looking for ways to stretch transportation dollars at a time when the nation’s highways have fallen into disrepair,” said Ed Patru, a spokesman for the group, in an interview earlier this year.

Patru said extending double trailers would cut around 6.6 million truck trips a year by increasing truck capacity by 18 percent. That would cut highway accidents attributable to congestion by more than 900 per year, he said.

One thing is for sure: more trucks are coming.

The Federal Highway Administration estimates freight traffic will increase to 29 billion tons in 2040, up from 20 billion tons in 2012. The agency sees the value of goods shipped rising even faster, to $39 trillion in 2040 from $18 trillion in 2012. Trucks handled about two-thirds of the tonnage and value in 2012, the FHWA said.

The American Society of Civil Engineers said in a 2013 report that 42 percent of the nation’s major urban highways are congested.

The Senate marked up a six-year surface transportation proposal in June, including a provision that would steer $2 billion toward freight projects.

But tax writers haven’t agreed how to pay for the $278 billion proposal, and many believe a short-term extension of current programs is likely through the end of the year.

With a highway bill off the table, the trucking coalition found a legislative vehicle for a trailer extension in the latest transportation appropriations bill (HR 2577). Longer trailers were also supported by the American Trucking Associations.

The extension is also an issue of profits: Longer vehicles can lower operating costs for trucking companies and boost profits.

That’s partly why Claybrook doesn’t believe longer trailers will reduce the number of trucks on the road or increase safety.

“Every time they try and argue for bigger, heavier, wider trucks, they say it’s going to result in less trucks. But it never does, it never has,” Claybrook said.

Opposition Raised

Not all trucking companies are on board with longer trailers.

A letter obtained by CQ Roll Call shows major carriers — including Knight Transportation, Swift Transportation, J.B. Hunt Transport and Heartland Express — urged Senate appropriators to oppose the extension, saying the change would “make it very difficult for small trucking companies, which are the heart of our industry, to compete.”

Lane Kidd, a spokesman for The Trucking Alliance, several of whose members signed the letter, said the provision would “transform the business model upon which all these carriers have structured what are multibillion-dollar companies.” He also questioned the provision’s impact on safety.

“It’s going to be up to the shippers of the country. The shippers are going to call their favorite trucking company and say, ‘Hey, are you guys going to start offering me these 33-foot trailers?’” Kidd said.

The Department of Transportation said it doesn’t have enough data to evaluate how changes would affect public safety and urged Congress not to make changes until better data is available.

The department expects to complete a long-overdue comprehensive truck size and weight study mandated in the last highway bill (PL 112-141) this year.

Lawmakers including Sens. Richard Blumenthal, D-Conn.; Roger Wicker, R-Miss.; and Dianne Feinstein, D-Calif., objected to the proposal.

Feinstein offered a proposal that would require the Transportation Department to prove no negative impact on public safety if trailers were extended, using the final truck size and weight study as proof. Appropriations Chairman Thad Cochran, R-Miss., supported the amendment.

“You want to take an eight-story building and put it on wheels and put it on the crowded freeways of America? That’s nuts,” Feinstein said.

Her amendment was rejected.