The new highway, which environmentalists fought for decades before its opening this year, attracted an average of about 21,000 vehicles per day -- just over the 20,000 officials expected.
About 326,000 cars took the ICC during the highway's first two weeks of operation after tolls were instituted along its newest section. Officials earlier predicted that the highway would see about 20,000 cars a day right after tolls kicked in and wouldn't see 30,000 cars until June.
Maryland Transportation Authority spokeswoman Teri Moss said the numbers were running "slightly" above projections.
The highway, which connects Interstate 270 in Montgomery County with Interstate 95 in Prince George's County, is the first in the state on which all tolls are collected electronically. Some drivers use E-ZPass. Those who don't have E-ZPass receive a bill for the toll in the mail.
But the highway's newfound popularity doesn't mean its opponents have accepted it.
"It's a beautiful road, but it comes at tremendous environmental and economic cost," said longtime ICC opponent Jim Fary, president of Neighbors of the Northwest Branch. "And now I think it's going to become [Gov. Martin] O'Malley's folly. It's economically unsustainable, and people are slowly waking up to that,"
Fary said he was riding in a shuttle to Baltimore/Washington International Thurgood Marshall Airport last week when his driver gushed about how convenient the ICC is -- until Fary told him that there was a toll, something the driver didn't realize.
"And when people realize that, they're in shock," said Fary, adding that he thinks that despite signs, the E-ZPass tolling means people don't immediately understand that the tolls can cost up to $4 per car during rush hour.
Greg Smith, an analyst for College Park-based Community Research and a vocal critic of the ICC, said the surprisingly high traffic numbers may not be all that high after all, because officials kept altering their projections.
"Typically they've aimed for the number of dollars they need to get and somehow, miraculously -- no matter what happens in the economy -- that's what they tend to get," he said.