Motorists traveling from Frederick to Rockville during the peak morning commute could end up paying $2.26 per mile — or nearly $50 total — to use the toll lanes being planned for Interstate 270, according to regional traffic models.

Morning commuters who use the Capital Beltway’s planned toll lanes to reach Northern Virginia could end up paying $1.66 per mile — or about $25 total — from Interstate 95 to the American Legion Bridge, according to an analysis by the Metropolitan Washington Council of Governments (COG).

Maryland highway officials are studying the potential effects of widening I-270 and the state’s portion of the Beltway to add up to two new toll lanes in each direction. The state has begun to solicit companies for public-private partnerships to build the estimated $10 billion worth of toll lanes, replace the American Legion Bridge with a wider one and rebuild the general lanes, which would remain free.

According to the COG models, the highest tolls would occur on segments of the highways with the worst congestion. That’s because the lanes would use dynamic tolling, with rates fluctuating based on congestion to keep traffic moving at a minimum of 45 mph. As the toll lanes grow more congested, the rates rise to encourage more motorists to use the regular lanes.

The COG planners said their computer modeling was not an “investment-grade” forecast but was a “good indicator” of which sections of I-270 and the Beltway would face “relatively high” toll rates based on their heavier traffic.

They said morning toll rates projected for the Beltway ranged from 20 cents per mile to $1.66 per mile, with the higher rates on the segment between I-95 and the American Legion Bridge. Morning toll rates on I-270 ranged from 20 cents to $2.26 per mile, with the higher prices in the peak southbound direction, using the COG models.

An analysis by the Maryland State Highway Administration predicts toll rates ranging from 66 cents to 77 cents per mile, according to the state’s federally required draft environmental impact statement, which was released in July.

Project opponents said they discovered the regional planners’ pricier estimates on Page 883 of a technical report in the state’s draft impact statement. Opponents have been scouring the document and its appendixes, which together number more than 19,500 pages, during the study’s public comment period, which ends Nov. 9.

“The Maryland [Department] of Transportation hid this bombshell revelation deep in the fine print of its Draft Environmental Impact Statement for the toll lane project,” the Maryland Transit Opportunities Commission said in a news release Thursday. “MDOT refuses to show the public its own calculations of future rush-hour tolls.”

Terry Owens, a state spokesman for the project, said the group’s assertion that motorists “will” pay the amounts projected by the COG is “inaccurate, misleading and suggests a lack of understanding” of the federal environmental review process. The final toll rates will be set by the Maryland Transportation Authority’s board after public hearings, he said.

The COG projections, Owens said, “are hypothetical toll rates with different data and assumptions than the state is using in the federal DEIS.”

Owens did not elaborate on how the data or assumptions differed.

One difference: The state’s projections were for 2025, while the COG estimates are for 2040.

Another apparent difference: The state’s study shows an “average daily toll rate” for different toll lane designs, over all time periods. Its projected toll rates also don’t pertain to particular road segments. The COG estimates apply to the morning peak and specific sections of both highways, resulting in higher toll rates for segments that are particularly congested during the morning rush.

Maryland Gov. Larry Hogan (R) has said teams of companies will build the lanes and finance their construction in exchange for keeping most of the toll revenue over 50 years, with the state paying nothing. The Washington region needs the lanes to relieve traffic congestion that pains motorists and threatens to stifle economic growth, Hogan has said.

Project opponents have said the toll lanes would be unfair to lower-income drivers, encourage auto-dependent sprawl development and destroy homes and environmentally sensitive park land.