The region’s top transportation board has endorsed a proposal for a network of trails stretching across the greater Washington region, from Frederick, Md., to Prince William County, Va., that would expand the amount of off-road bicycle and pedestrian pathways to 1,400 miles.

The extensive trail system would more than double the size of the existing network by adding 755 miles to the current 645 miles of trails, improving connectivity between neighborhoods and public transit, commercial districts and jobs, said officials with the Transportation Planning Board (TPB) of the Metropolitan Washington Council of Governments.

The proposal would offer greater access to clean, inexpensive and reliable transportation to millions of area residents seeking options beyond vehicles and public transportation, board members said.

“Once we get those connections made, we will see that having a complete interconnected network where you can get onto a low-stress facility within relatively short distance from your home and go to almost everywhere in the region will be really transformative,” Michael Farrell, a board transportation planner, said at the panel’s July 22 meeting where a resolution approving the trail network was adopted unanimously.

Once the expansion is completed, more than 4 million people in the Washington region will have access to trails within a half a mile of their home, according to a TPB analysis. Trails would also be within reach of more than 2.5 million jobs and 136 of the region’s residential and business centers. The board, composed of mayors, supervisors, council members and other local government officials, envisions completion of the trail network within 25 years.

The 1,400-mile trail expands upon the vision laid out by the Capital Trails Coalition, a group of more than 60 nonprofits, business and government agencies that have been pushing for a connected multiuse trail system of 900 miles across jurisdictions close in to the District. The coalition has closely worked with the TPB in recent years to move the plan forward, and the proposal adopted is an expanded version of that vision. In 2018, the TPB adopted a regional trail plan connecting 60 miles of jurisdictions in the region’s core.

The adoption of the Capital Trail Network map is key to ensure that localities and the region prioritize funding of trail projects over the next decades. Most of the proposed bike and pedestrian paths are already in the plans of transportation, parks and planning departments in the region.

Liz Thorstensen, vice president of trail development at the Rails-to-Trails Conservancy and chair of the Capital Trails Coalition, said the board’s adoption of the map shows a long-term commitment to building a seamless regional trail network across jurisdictional lines. Even more importantly, she said, it shows a commitment to finding potential funding streams to help that happen.

“This is just wind in our sails to keep going,” Thorstensen said. She said the coalition has momentum to get more elected leaders, residents and trail users, and major employers to get behind the vision.

Political support is critical to ensure that trail projects can compete with other transportation projects that have taken priority over the years, such as fixing and building roads. Transportation advocates and officials say it has become clearer during the coronavirus pandemic that demand for trails is high and that they can take an important role in moving people around the region.

“People have turned to biking and walking [for] recreation and also as a way to get around,” said College Park Mayor Patrick L. Wojahn, who is also a member of the transportation planning board. Wojahn said the adoption of the regional trails map is “very timely” as the region rethinks its transportation in the post-coronavirus era.

“As the pandemic continues to impact our communities,” he said, it has become clear “how important it is to be able to have opportunities to get out safely, walking and biking.”

Thorstensen said demand for trail use was there even pre-covid-19, but it has become more urgent now as people seek places to be outside and socially distant.

The plan does not set a dollar amount on the cost of building the entire network. Cost is specific to each project, the site conditions and the additional amenities local agencies choose to build, officials said.

The trails coalition last fall, however, offered some insight on the price. Building the roughly 400 miles missing from the 900-mile network in the Washington core — including the District and the city of Alexandria as well as Arlington, Fairfax, Montgomery and Prince George's counties — would require just over $1 billion, according to the coalition.

Proponents and board officials say trails are a low-cost option, especially compared with much more costly road and transit projects. For example, the plan to rebuild and widen the American Legion Bridge connecting Maryland and Virginia is a $1 billion project. The widening of 22.5 miles of Interstate 66 in Northern Virginia to add toll lanes cost nearly $4 billion. Maryland’s proposed widening of the Capital Beltway and portions of Interstate 270 has a price tag above $9 billion.

As the region continues to grow, elected leaders have been promoting cycling and walking as a potential solution to reduce traffic congestion and its carbon footprint and to promote healthier lifestyles. A report by the Rails-to-Trails Conservancy estimates that the Washington region would record $500 million a year in health-care cost savings if it completed the trail network.

The Transportation Planning Board staff is expected to use the adopted trail map to prioritize funding for projects. Staff will also report to the board on progress toward implementation every year.

“The TPB expects its member agencies will make this investment a priority and hopes the region will realize this as expeditiously as possible,” Farrell said.

Earlier versions of this article incorrectly attributed the final quote to Megan Goodman, a spokeswoman for the Council of Governments.