The 29-mile Baltimore-Washington Parkway has connected the two cities since 1954. iStock

The analysis, commissioned by The Pew Charitable Trusts, looked at five popular parkways, four of them in Washington metro area. The cost of addressing deferred maintenance needs in national parks is approaching $12 billion, about half of which is attributed to transportation infrastructure. The five parkways listed below need more than $533 million in repairs.

The National Park Service (NPS) could generate $16 million to $190 million annually by collecting tolls on some of the parkways it oversees—money that could help pay to maintain and repair those roads, a study found. Currently, the NPS lacks the legal authority to collect tolls.

The four Washington area roads were designed as scenic routes but are often jammed with commuter traffic. The fifth road studied, the 469-mile Blue Ridge Parkway, which runs from Afton, Virginia, to Cherokee, North Carolina, was the most-visited NPS site in 2017 with more than 16 million visits.

The analysis looked at tolling structures of 4, 8, 12, or 16 cents per mile, as well as a modest flat-fee model. Results varied by parkway, with the highest potential revenue measured on the Baltimore-Washington and Suitland parkways.

This study was not intended as a policy recommendation but was conducted to determine whether tolling would be a way to help fund park repairs. Preliminary findings show that, under certain circumstances, it could provide a viable option.

Marcia Argust directs The Pew Charitable Trusts' campaign to restore America's parks.