For more than a century, the Long Bridge has carried freight and passenger trains across the Potomac River between Crystal City and the District’s Southwest Waterfront, facilitating rail transportation along the Eastern Seaboard.

Officials say the bridge, a key piece of the Interstate 95 corridor’s rail network, needs to double its capacity if it is to continue to support commerce and the increasing demands for passenger rail along the East Coast.

The bridge’s two-track configuration creates a bottleneck in the system as trains funnel from three tracks to two, slowing the movement of freight and passengers along the corridor. A fourth track is planned to be added south and north of the bridge, which would create an even more significant choke point, transportation officials said.

The only solution, they say, is to add two tracks and create a four-track crossing over the Potomac to handle more commuter and intercity rail service as well as expected increases in freight transportation over the next decades.

“Within the next five to 10 years, we need to be able to run more trains to keep up with the demand,” said Jennifer Mitchell, director of the Virginia Department of Rail and Public Transportation. “But until we expand that bridge, we are not going to be able to expand passenger rail in the region.”

The Federal Railroad Administration and the District Department of Transportation are leading a federal environmental study that could determine the future of the bridge. They recently unveiled a plan to keep the Long Bridge and build a two-track bridge next to it to create a four-track crossing. The project would take five years and cost $1.3 billion to $1.6 billion.

Another alternative is to build two, two-track bridges to replace the Long Bridge. However, that option would cost between $2 billion and $2.3 billion — and would take up to eight years of construction, according to government estimates.

Earlier this year, officials ruled out the idea of building a four-track bridge. A study determined that four tracks on a single structure would result in more slowdowns during planned maintenance or for an unanticipated outage on any one track.

The plan favored by FRA and DDOT — keeping the Long Bridge and building a second bridge next to it — would not only keep costs lower, but it would also lessen the impact on the environment, historic property and parkland in the area, they say.

A stand-alone bike and pedestrian bridge would be built upstream from the new rail bridge, allowing people to walk or bike across the Potomac between two of the region’s fastest growing areas — the city’s thriving waterfront and Crystal City in Arlington, which will be home to a new Amazon headquarters and an anticipated 25,000 jobs.

“This project is a once-in-a-lifetime opportunity to provide the safest option for bicycles to cross the Potomac on the day it opens,” said Robert Gardner, advocacy director at the Washington Area Bicyclist Association.

Improving the Long Bridge for future use is a good investment for the U.S. economy and for safety and mobility, especially with Washington’s traffic congestion, railroad and transportation officials say.

The bridge is a literal connection between the Northeast and Southeast corridors, and restrictions on the number of passenger trains allowed to use it affects plans for the growth of intercity service across the region. Virginia’s vision for more robust passenger and commuter rail service across the state depends on the Long Bridge expansion, Mitchell said.

“The Long Bridge is really at capacity, especially during the peak hours, and it is our biggest bottleneck in the state,” she said. “For us to expand anywhere, we really need to expand the bridge.”

Adding more passenger service over the Potomac in the next decade, she said, will be necessary to meet the demand driven by population growth, economic growth and congestion. Highway projects such as the addition of high-occupancy toll lanes on interstates 95 and 66 in Northern Virginia are not going to be enough to handle the growth, and building more lanes is not feasible, officials say.

“The best ways for us to provide transportation capacity in those corridors is through rail,” Mitchell said.

DDOT Director Jeff Marootian agrees the project is important for congestion relief. The expectation is that improvements to commuter rail coupled with the addition of the pedestrian and bike path will help reduce the volume of cars entering the District, he said.

“It’s a win for us and our neighbors,” Marootian said.

The Federal Railroad Administration is expected to release a draft environmental assessment next summer and a final recommendation in 2020. If the project wins federal approval, it could be another two years of design before construction begins, officials said.

Funding for the project has not been identified. But as the study moves forward, officials in the District and Virginia say they will be working as a region to secure grants and have a funding plan in place by the time the study is complete. Virginia rail officials say $30 million has been budgeted for design and engineering — $15 million from state rail funding and a $15 million pledge from CSX Transportation, which owns the bridge.

A demand for more

The Long Bridge first opened in 1809 and was used during the Civil War. It was damaged by fires and floods several times during the 19th century and rebuilt. The current steel-truss two-track bridge opened in 1904, spanning just over 2,500 feet.

Railroad officials say the 114-year-old bridge is sound and can handle freight traffic for the foreseeable future. CSX, which acquired the bridge in 1999, completed a rehabilitation in 2016, lengthening its life span. But it is still outdated and at about 98 percent capacity. Because of its condition, there are speed restrictions on the tracks approaching it, further limiting operational capacity, according to a DDOT report.

“The Long Bridge in its current form is sufficient for our freight volume,” CSX spokeswoman Laura Phelps said. But, she said, the railroad supports federal and local efforts to increase capacity over the Potomac for passenger trains.

The tracks are used by CSX, Virginia Railway Express and Amtrak. On a typical weekday, 76 trains travel across it, of which nearly half carry Northern Virginia commuters into the District.

By 2040, volume on the bridge is projected to increase by 150 percent, according to a project report.

Each day, VRE transports about 20,000 passengers on 34 trains to and from the District, a number that is projected to grow to 92 trains by 2040. Amtrak’s daily trips could grow to 44 trains from 24 as plans advance for higher-speed intercity trains between Washington and Richmond.

If nothing is done, the reliability of the passenger service in the corridor could significantly decline. Federal reports project VRE’s on-time performance could drop to 25 percent by 2040, from 91 percent today, while Amtrak’s on-time performance could drop to 12 percent from 70 percent.

VRE is counting on the bridge expansion to fulfill its long-term vision to not only add more trains to its peak-direction service from Manassas and Fredericksburg to the District and back, but also reverse-peak and express trains by 2030.

The expanded capacity also would open the possibility for Maryland MARC trains to travel past Union Station into Virginia and VRE trains to serve stations in Maryland, transportation officials say.

“Without that extra capacity, we are limited in being able to run any more trains,” VRE chief executive Doug Allen said, noting that its trains are already largely at capacity. “There is a real demand for more of our service, which is why this project is critical for us to be able to run more trains and provide more people the options for getting into D.C. and getting back out again.”