Photo by bankbryan on Flickr.

I-95 in Northern Virginia is already one of the nation’s most congested corridors, and forecasts predict it will only get worse. A new study by the GMU Center for Regional Analysis lays out the difficult decisions area leaders face regarding the corridor’s future land use, economy, and transportation network.

At present, the I-95 corridor in Fairfax and Prince William counties is mainly a low-density suburban area. Most residents work in DC, Arlington, or Alexandria, and existing transit such as the Blue Line and VRE only serve inside-the-Beltway locations. The area’s lone major employment center is Fort Belvoir, which is spread out and has limited bus service.

Traffic volume and congestion along I-95 are already very high, and major road investments are not expected to reduce congestion. Furthermore, job growth in the region has been occurring in areas like Tysons Corner and the Dulles Corridor, which are hard to reach from the I-95 corridor, especially by transit.

Development plans along the corridor envision a series of dense urban nodes around transit in places like Springfield, Huntington, and Woodbridge. But the success of those areas depends on carefully planned, and expensive, transportation investments both within the corridor and to other areas.

The situation is already problematic

The 21-mile stretch of Interstate 95 that connects the Capital Beltway and Quantico is one of the busiest highways in the eastern United States. The most heavily traveled segment of the corridor, located just south of Old Keene Mill Road, carries an average of 231,000 vehicles per day. This count includes about 30,000 vehicles per day in the corridor’s reversible express lanes and about 14,000 tractor-trailers.

Traffic volumes along the corridor tripled between 1975 and 2000, but have flattened out since then. That’s due to the expansion of transit and, more recently, the rerouting of through traffic around the “Mixing Bowl” interchange in Springfield.


All images from the GMU Center for Regional Analysis unless noted.


Transit ridership in the corridor has increased dramatically over the past 15 years, with the average number of daily boardings on the Virginia Railway Express (VRE) tripling and the number of boardings at the Franconia-Springfield Metro station increasing by 48 percent. The corridor also contains more than 15 express commuter bus routes that connect it to the Pentagon, downtown Washington, and Tysons Corner. In total, about 27,000 transit riders per day make use of these rail or bus options to travel to work each day.

Surveys by transit operators show that the majority of these riders work for the federal government and routinely commute by transit four or five days every week. These transit options are becoming increasingly congested: VRE reports that its trains operate at as much as 20 percent over capacity during peak times.

Increased traffic in the corridor has been a function of commuting patterns. Since 1990, the number of people who live in Fairfax or Prince William and work in DC, Arlington, or Alexandria has remained flat, while the number who work in other locations increased by more than 100,000 people.

Nearly all existing transit in the I-95 corridor serves employment hubs located inside the Beltway, so few options exist for these commuters. Traffic has also increased due to additional commuting activity from Stafford, Fredericksburg, and points south.

Lots of growth, little land

The areas of Fairfax and Prince William around I-95 are primarily residential: the Metropolitan Washington Council of Governments (MWCOG) reports that the corridor contained 566,000 residents and 187,000 jobs in 2010. Most corridor residents live in low-density, single-family areas, and there is little undeveloped land remaining in the area. MWCOG forecasts that the corridor will add another 126,000 residents and 85,000 jobs by 2030. Where will they go?


MWCOG Traffic Analysis Districts (TADs)


A look at the Comprehensive Plans for the two counties provides some clarity. Each county has designated a small number of areas located directly along I-95 and/or around transit stations for mixed-use development.

Fairfax anticipates high-intensity residential and commercial development around the Huntington and Franconia-Springfield Metro stations. Meanwhile, Prince William is planning intensive growth around the Woodbridge VRE station and a potential future VRE station at Potomac Shores, north of Quantico.

But the county also wants growth at the more auto-dependent Parkway Employment Center, north of Potomac Mills, and Neabsco Mills, south of Woodbridge along Route 1. Since VRE has no immediate plans to expand service on the Fredericksburg Line, additional growth in these areas would further strain the already-crowded system.

Investment in roads and highways isn’t enough

The Virginia Department of Transportation (VDOT) is in the midst of completing a slate of “megaprojects” in the corridor. Two of these are already in place: the widening of I-95 between Route 123 and the Fairfax County Parkway, and the completion of the last segment of the Fairfax County Parkway, encompassing a network of new roads, interchanges, and trails around the Fort Belvoir North Area.

VDOT reports that these new facilities have slightly reduced congestion in this segment of the corridor. But these investments have not reduced congestion in adjacent areas and may have even worsened it by allowing more vehicles to enter and exit the highway.


Construction on the I-95 express lanes. Photo from VDOT.


VDOT’s most ambitious project in the corridor is a $1 billion expansion of the I-95 express lanes. This project will extend the express lanes nine miles into Stafford County, add a third lane north of Prince William Parkway, and connect the express lanes with the I-495 express lanes. It will also convert the express lanes from HOV to high-occupancy toll (HOT) lanes from Stafford County to Edsall Road, just inside the Beltway. The express lanes will remain as HOV-3 lanes along I-395 north of Edsall Road.

The express lanes project will unquestionably add highway capacity, but will it actually reduce congestion? A serious concern is that converting the existing HOV lanes to HOT lanes will very likely reduce carpooling activity, as people driving alone will be able to pay to use the express lanes. A reduction in carpooling translates to needing more vehicles to move the same number of people, contributing to additional congestion.

VDOT’s own Environmental Assessment of the I-95 express lanes concluded that, while the project would improve the overall situation, several currently failing road segments would remain at failing levels. It further concluded that, after completion, the merge areas at the northern and southern ends of the HOT lanes would still operate at failing levels.

Clearly, even this billion-dollar project will not solve the traffic woes faced by I-95 corridor commuters. Additionally, this project is primarily aimed at moving commuters through the corridor, and does not address the need to better connect the emerging urban nodes in the two counties to each other or to the surrounding region.

So what can be done?

To their credit, both Fairfax and Prince William counties have committed to focusing future development around existing infrastructure. However, successfully clustering new development in this manner will create a complex set of challenges.


Improving transit connections to far-flung employment centers can reduce traffic. Photo by Elvert Barnes on Flickr.


The counties will need to provide transit that serves private-sector workers, particularly those with irregular hours and/or in dispersed locations. They will also have to improve access to existing and planned transit hubs from nearby neighborhoods and employment centers.

It’s also necessary to attract the high-paying office jobs that planned suburban employment nodes will need, and to provide housing that matches up with those jobs’ earning potential to allow for shorter commutes.

Once those jobs are in place, Fairfax and Prince William need to create new incentives to encourage carpooling, and to add capacity to the I-95 corridor’s already strained and crowded transit systems. The counties will also have to work regionally to help address transportation problems that originate elsewhere but affect the corridor.

Continued congestion of highways, roads, and transit in the I-95 corridor threatens its prosperity. Public and private sector leaders at both local and regional levels will need to understand and address the above issues in order to achieve their bold visions for future development.