Loved or loathed, needed or not, the Intercounty Connector toll road is scheduled to open two days before Thanksgiving and several weeks ahead of schedule.

The opening of the road that will link Interstate 370 in Gaithersburg and Interstate 95 in Laurel will help settle one of the longest-running debates in the region’s transportation history: Will the $2.56 billion road alleviate congestion or create more by inviting more suburban sprawl?

After decades of acrimony that has involved transportation planners, developers, smart-growth proponents, residents, environmentalists and champions of mass transit, it’s unlikely that the most strident advocates will find consensus on the effect of the highway.

That question will be answered by drivers and the people who live there.

Motorists will get first crack at a new 10.35 miles of the ICC — 7.2 miles opened in February — on Nov. 22, and they will be able to traverse it for free before tolls take effect Dec. 5.

“One of the things we had hoped for was to be open before Thanksgiving weekend,” said Harold M. Bartlett, executive secretary of the Maryland Transportation Authority. “It’s one of the biggest travel days of the year.”

The new portion of the highway had been projected to open by year’s end or early in 2012. Bartlett said that despite a fair amount of rain this year, construction kept pace and good management got the job done ahead of schedule.

“I can’t think of any other major highway in the country that has opened on time and on budget,” he said.

A final spur that would connect I-95 with U.S. Route 1 in Prince George’s County remains to be built. Bartlett said he would be better able to set a completion date for the last segment by the end of the year. “We’re reasonably confident that we’ll be able to do that . . . and inside the funding envelope for the highway,” he said.

The ICC is a toll road without tollbooths.

The passage of each car is recorded electronically, primarily through the use of E-ZPasses. For vehicles without an E-ZPass, a camera records the license plate number and the toll charge arrives in the mail with a service fee. Now, vehicles without E-ZPasses are charged an extra $3, but that will be replaced by Tuesday with a statewide “video toll rate,” which will be 150 percent of the base fee, part of a package of toll changes throughout the state.

“We’re trying to strongly encourage people to get an E-ZPass,” Bartlett said.

Although no tolls will be charged from Nov. 22 to Dec. 4, drivers who use the ICC without an E-ZPass will receive a notice in the mail urging them to get one.

The ICC uses variable-priced tolling, charging different rates to cover the same distance, depending on the time of day. Under the three-tiered program, passenger vehicles pay 25 cents per mile at peak hours, 20 cents per mile during off-peak and 10 cents per mile during overnight hours.

Signs posted at entrances to the highway alert drivers about which tolling period is in effect.

Bartlett said the toll would be $4 for a passenger vehicle to travel the ICC from end to end during peak hours.

The origin of the six-lane highway traces to the mid-20th century, when the Capital Beltway was being completed and planners envisioned a second outer ring of superhighway around Washington. They thought most of it would be finished by 1970.

But the proposal drew powerful opposition from environmentalists and residents who feared it would pollute the air and streams and eventually cause more congestion by encouraging development.

The right of way for much of the highway was bought before the surrounding area was developed, so construction didn’t require razing as many homes as might have been the case in more densely settled suburbs.

The new highway is little more than half as long as the one promised in 1958, which was to sweep in a 32-mile arc from just north of Potomac to Bowie.

Staff writer Katherine Shaver contributed to this report.