New toll lanes kicked off Monday morning along a 10-mile stretch of Interstate 66 in Northern Virginia. At first blush, the rates seemed rather high.

The estimated toll for one-way travel from the Beltway to Washington before 8 a.m. was $28.50. About 8:40 a.m., the toll was $34.50.

The rates are variable depending on traffic conditions. Officials with Virginia’s Department of Transportation said the $34.50 rate was the “peak of the peak rate.”

“It is a dynamic toll,” said Jenny McCord, a spokeswoman for VDOT. “It will vary and fluctuate based on the demand.” Other times, she noted, the toll was in the low $20s. The toll changes every six minutes.

The new toll lanes run from Route 29 in Rosslyn to Interstate 495. They are meant to help alleviate traffic along one of the most congested roadways in the region.

Tolls kicked in for the afternoon rush at 3 p.m. Monday. Rates were lower than the morning commute, with westbound I-66 drivers paying $6.25 to travel from Washington to the Beltway at 4:15 p.m.

The new toll lanes are similar to those found on 495 and the 95 Express Lanes. Solo drivers can use the new HOT lanes — high occupancy toll lanes — during rush hours as long as they’re willing to pay the toll.

Previously, there were HOV restrictions that limited the use of that section of I-66 during rush hour to vehicles with two or more people and drivers of hybrid vehicles with special clean-fuel license plates.

There is no cap on the toll pricing. The price changes as congestion rises and decrease as congestion is less. The hours of the toll lanes are from 5:30 to 9:30 a.m. eastbound and 3 p.m. to 7 p.m. westbound, Monday through Friday. The lanes are free to all drivers during off-peak hours and weekends.

Transportation leaders have said they expect the new tolls to encourage carpooling and to push more people to use mass transit. When tolling was talked about in 2015 and models on traffic and pricing were done, transportation officials had said that, on average, the price would average about $9 for the 10 variations of trips drivers could take on the highway.

Part of the reason toll prices can spike at any given time, VDOT officials said, is that the system bases rates on the volume and speed it is trying to maintain. On Monday, VDOT said the average speed was 57 mph, compared to 37 mph at roughly the same time a year ago.

McCord said VDOT expected to have more detailed numbers later today on how the first day of the tolls went. Overall, she said, transportation planners felt that the new toll had done its job — to help provide a more reliable trip. But at a cost.

New toll lanes kicked off Monday morning along a 10-mile stretch of Interstate 66 in Northern Virginia. (Jahi Chikwendiu/The Washington Post)