Rush-hour traffic is backed up along Interstate 66 in this view from the Vienna Metro Station in May. (Nikki Kahn/The Washington Post)

The recently announced compromise on fixing Interstate 66 inside the Beltway is a responsible solution to an obvious problem irresponsibly ignored for too long.

The decades-old decision limiting this roadway to two lanes in each direction was made by politicians, not the planners who said four lanes in each direction were needed to meet 21st-century travel demand. Time has proved the planners right. This highway is congested not only at rush hour but also throughout the day and on weekends. This solution would improve travel reliability at all times.

Gov. Terry McAuliffe (D), Transportation Secretary Aubrey Layne, Dels. James M. LeMunyon (R-Fairfax) and David L. Bulova (D-Fairfax) and Sen. J. Chapman “Chap” Petersen (D-Fairfax) are to be commended for helping to forge a solution that will improve travel reliability.

Now, two eastbound I-66 inside-the-Beltway lanes are required to handle volume from three eastbound lanes outside the Beltway, the eastbound lanes of the Dulles corridor and Beltway and local street traffic. Not surprisingly, they fail regularly.

By constructing a third eastbound lane between the Dulles Connector Road and Ballston, the compromise would unlock one of the region’s worst transportation choke points for motorists, and the tolls would add tens of millions of dollars to support expanded transit services.

The Texas A&M Transportation Institute reports that area commuters waste the most time in traffic in the nation. The Virginia Department of Transportation’s analysis shows a third eastbound lane and expanded transit services would save travelers 26,000 hours a day in delays. Combined with I-66 express lanes outside the Beltway, commuters would save 31,000 hours a day.

While outside-the-Beltway residents would certainly benefit, but Arlingtonians may benefit most because the compromise would remove regional traffic from neighborhood streets and improve transit and auto access to a major economic driver, the Ballston-Rosslyn corridor.

The Census Bureau’s American Community Survey also shows most Arlington workers live outside Arlington and most Arlington residents work outside Arlington. The I-66 compromise would make it easier for non-Arlington residents to get to Arlington jobs in the morning and for more Arlington residents working outside the county to get home earlier to their families.

Claims that the project “paves over Arlington” are without foundation. A third westbound lane already exists, constructed within the existing right of way and without taking any homes. This can be replicated in the eastbound direction.

The District would benefit from improved access, although studies show a high percentage of eastbound traffic is Ballston/Rosslyn-bound.

Tolls would apply only to single-occupant drivers opting to pay to travel during time periods not currently available to them. Violators no longer get a free ride. Good!

If approved by the Virginia General Assembly, this compromise would improve the region’s mobility, economic competitiveness and quality of life. But it’s not a done deal. The right budget amendments must be approved by the General Assembly; bad amendments could kill the compromise. This must not happen.

The compromise proposal is not perfect, but it is far better than anything thought achievable just a few weeks ago. If it is allowed to fall apart, the damage to the region would be immeasurable.

Prosperity cannot be taken for granted. If Northern Virginia is to maintain its position as one of the most attractive places to live, work and do business, the pragmatic, bipartisan spirit present in the I-66 compromise must be applied to overcome other long-standing transportation impediments to our economic prosperity and quality of life.

The writer is the chief executive of the Northern Virginia Transportation Alliance.