Looking east on Interstate 66 from the North Scott Street overpass, traffic is seen Monday evening in Arlington. (Jahi Chikwendiu/The Washington Post)

On the fourth day of tolling on Interstate 66, the morning price peaked at $25.50 around 8:30 a.m.

Virginia Department of Transportation officials rolled out the new express lanes inside the Beltway on Monday. And their debut has been met with mostly price shock from drivers.

At one point this week, the toll — a dynamic pricing system based on demand levels, changing every six minutes — hit $40 for the 10-mile route between the Beltway and the District.

Carpoolers, using the proper EZPass setting, were exempt from the toll.

Tolls were expected to be between $7 and $9 during morning and evening rush hours, when the concept to open the roadway to non-carpoolers during rush hour was first pitched by state officials. Before this week, solo drivers could not legally drive the stretch of I-66 during designated hours.

Transportation officials this week have said the tolls are meant to encourage solo drivers to carpool or use slug lines or public transportation. Some drivers have reacted to the new pricing on social media with the hashtag #highwayrobbery.

On the roads, drivers have said they’ve noticed what feels like increased traffic along other routes near I-66, including Route 123 and the George Washington Parkway.

Although transportation officials at VDOT said they don’t yet have exact numbers and analysis on how many people are using the new toll lanes, the prices — and volume of vehicles — on them will likely vary greatly. Mondays and Fridays tend to be lighter traffic days in the region, whereas Tuesday, Wednesday and Thursday are heavier commuter days, experts have said.