Traffic on the Intercounty Connector from the Needwood Road overpass in Rockville, Md. (Mark Gail/The Washington Post)

Welmoed Sisson’s drive between her northern Montgomery County home and her business clients across the Maryland suburbs often includes a trip on the Intercounty Connector, a toll highway with so little traffic that Sisson can’t recall ever tapping her brakes.

Almost 19 miles of pavement with no one in her way. Ever. Not even at rush hour.

“It’s not an empty wasteland,” said Sisson, 54, who owns a home inspection business with her husband. “But it’s certainly nowhere near the volume of the free roads in the area. . . . It’s nice, but then again, you’re paying for that quiet.”

Sisson said the 20 minutes or more she can save and the stress-free drive are worth the $50 in ICC tolls her company typically pays every month. But the amount of open asphalt that remains on the ICC nearly four years after it first opened is prompting some to urge Maryland Gov.-elect Larry Hogan (R) to cut toll rates, particularly for regular commuters.

They say the Washington area’s traffic congestion is too severe to allow a six-lane highway to go significantly underused. The ICC, they say, could absorb far more traffic from heavily congested local roads in Montgomery and Prince George’s counties until the growth the highway was built to accommodate arrives. Tolls could be increased again over the years, they say, to keep it free-flowing as traffic builds.

Using the entire 18.8-mile highway between Interstate 270 in Gaithersburg and U.S. Route 1 in Laurel during rush hours costs $4.40 each way for passenger vehicles and $32.90 each way for the largest tractor-trailers.

“Its purpose is to relieve congestion,” said Marilyn Balcombe, president of the Gaithersburg-Germantown Chamber of Commerce, which pushed for the ICC’s construction. “If there were lower tolls, more people would use it, so it would relieve more congestion [on local roads] and meet the original purpose of the road.”

Maryland Transportation Authority officials say they can’t lower the ICC tolls without losing revenue needed to pay off the road’s construction debt. They also say the ICC remains on target for its volume and revenue projections.

However, a Washington Post analysis found that’s only because the state’s consultant downgraded those estimates over time. The projections that Maryland lawmakers had in 2005, when they agreed to pay for the ICC’s $2.4 billion construction by charging tolls and taking on heavy debt, were much rosier.

Compared with initial forecasts, the ICC had about half as many vehicles and brought in $19 million less in toll revenue last fiscal year than was projected, the Post found.

Maryland Transportation Authority officials say the ICC is successful, noting that an average 50,000 vehicles used it daily in the fiscal year that ended June 30.

“Fifty-thousand vehicles per day is not empty,” said authority spokeswoman Kelly Melhem.

Melhem said it’s inaccurate to compare today’s ICC’s traffic volume and toll revenue with early forecasts because those estimates didn’t anticipate the recession of 2008 and 2009. Some early projections also were based on higher toll rates than those now in effect and anticipated the full highway opening at once rather than in segments, as it did. The first two segments opened in 2011, and the final 1.5-mile piece between I-95 and U.S. Route 1 opened Nov. 10.

“It’s designed for traffic in 2030, so we certainly wouldn’t have wanted to build a road that became congested immediately,” Melhem said.

The ICC is the only Maryland toll facility that doesn’t give steep discounts to commuters, although the soon-to-open express toll lanes on Interstate 95 north of Baltimore also won’t offer them. A rush-hour commuter who uses the entire ICC daily would spend $2,200 annually.

“The ICC had the public support it did because people felt it would be used by a large number of people,” said Montgomery County Council Member Phil Andrews (D-Gaithersburg-Rockville), a longtime ICC critic. “There’s a way to greatly increase the use, and that’s by lowering the tolls.”

Hogan spokeswoman Erin Montgomery said the governor-elect won’t publicly discuss the ICC toll rates or any policy specifics until he takes office Jan. 21.

The highway did achieve a financial milestone in its second full fiscal year. For the first time, its toll revenues — $51 million — covered its operating expenses and debt service on the toll-backed bonds, meaning it required no subsidies from other state toll facilities. The authority has spent about $3.2 million to market the ICC to motorists, Melhem said.

But other financial impacts of the ICC, the most expensive highway ever built in Maryland, will continue to be felt statewide for years. That’s because the authority also financed the ICC’s construction with bonds backed by Maryland’s future federal highway funding. Payments on those bonds amounted to $87.5 million last fiscal year — about 15 percent of Maryland’s annual federal highway funds.

State officials also attributed two recent statewide toll increases — tolls on the Chesapeake Bay Bridge more than doubled — in part to the need to pay off construction debt on the ICC and the new Interstate 95 toll lanes.

Reducing the ICC tolls could require the authority to cover the ICC’s construction debt with more statewide toll revenues — a move unlikely to win political support from toll payers on the Eastern Shore and in the Baltimore area. CDM Smith, a Connecticut-based consultant for the authority, found in July 2013 that reducing the ICC toll rates would increase traffic but not enough to offset the overall losses in toll revenue.

Balcombe said the state could lower ICC tolls and still pay off the construction debt by restructuring lower payments over more years or using other state money.

John Townsend, a spokesman for AAA Mid-Atlantic, which pushed for the ICC’s construction, said the state’s ICC projections “overstated” the number of motorists willing to pay such “pricey” tolls.

“I think it will eventually meet all the expectations, but I think it will probably be another decade,” after areas around the highway develop more, Townsend said. “On the front end, it’s proven to be very costly.”

Those willing to pay the ICC tolls delight in its wide-open feel. The only downside: Many say they must set their cruise controls or risk speeding tickets because there are too few cars around to help gauge their own speed.

Sisson’s 23-year-old daughter, Diana Sisson, called the ICC a “godsend.” She said she spends about $180 per month in tolls because it can cut more than an hour off her commute between Germantown and her job as a research assistant for a nonprofit company in Crofton.

“I get on the ICC, and I relax,” Diana Sisson said. “There’s usually not the sound of another engine next to me. I have a nice quiet 15 to 20 minutes.”