Looking east onto I-66 from the N. Scott Street overpass, traffic is seen Monday evening in Arlington. (Jahi Chikwendiu/The Washington Post)

Day 3 of new toll lanes along Interstate 66 came with lower prices for Northern Virginia drivers than the previous two mornings.

The toll appeared to peak around 9 a.m., when the cost of driving from the Beltway to Washington was $23.50. Tolls are based on a dynamic pricing system and fluctuate every six minutes.

Since their debut Monday, many drivers have expressed frustration and price shock at the high toll rates. The toll peaked at $34.50 on Monday and $40 on Tuesday, making I-66 among the highest-priced toll roads in the country.

On Wednesday after 8 a.m. — 24 hours after the toll reached $40 — a solo driver was paying $15.25 to use the 10-mile stretch of road.

Reaction on social media has given the new, expensive tolls the hashtag #highwayrobbery.

Transportation planners say the pricing is based on demand. And they say tolls are meant to encourage drivers to carpool, ride-share, use slug lines or take Metro. The toll pricing is locked once you get on the road.

Virginia Department of Transportation officials had said the tolls would peak around $7 for the morning rush and $9 in the afternoon when they originally pushed for the toll system years ago.

Jenny McCord, a spokeswoman for VDOT, said Wednesday that the toll system has gone through its fifth rush hour, but it will still take a week or two to determine out how things are going and another month to get a sense of new driver patterns.

She said VDOT wouldn’t have details on the number of drivers on the new toll road until early next week.

McCord said the $40 price that has been seen is only being paid by a small number of drivers. Those who are paying $40 are solo drivers who weren’t able to use the lanes before, she said. The prices spike because it is letting “people know the lanes are starting to fill up.”

“That’s meant to discourage people from getting on,” she said.

Motorcycles and vehicles carrying two or more people have free use of the lanes. The shift to HOT lanes gives solo drivers the option to use I-66 during rush hour — if they pay.

Some drivers have complained that other area roads are getting more crowded as some people try to avoid the tolls.