The Leesburg Pike Line, or 28A route, is the only service that spans a congested 13-mile corridor on Route 7. Transit advocates say the route is in great need of improvement (Luz Lazo/The Washington Post)

Route 7 is, in many ways, Northern Virginia’s main street, stretching nearly 73 miles from downtown Winchester to Alexandria.

The state highway and major commuter route passes through a booming job hub, shopping centers and residential communities, and it is among the region’s most traffic-choked. A 13-mile portion between Tysons Corner in Fairfax County and Alexandria is one of the worst. The roadway’s design, which shrinks from four lanes in each direction in Tysons to one in Alexandria, produces unavoidable bottlenecks. And despite a high reliance on transit along that heavily traveled portion, the stretch lacks bike paths, bus shelters, and, in some places, sidewalks and ramps needed for accessibility.

Some transportation advocates want to make the corridor a priority for improvements benefiting drivers and transit users, and the Northern Virginia Transportation Commission has ordered a study to find solutions for easing travel there.

“What we see is a tremendous need for improvement,” said David Snyder, the commission’s chairman and vice mayor of Falls Church. “There is obvious congestion and unappealing transit alternatives.”

In addition to improving bus service, the study will examine two options that are more costly and complex: a bus rapid-transit line and light rail. Both could require taking a lane from general traffic, which would be popular among transit riders but not with drivers.

Transit advocates say that all of the ideas are worth exploring. At the very least, bus service should be expanded along the route, which handles more than 6,300 rides daily. Riders have been asking for more frequent service with better connections to Metrorail, along with transit facilities that incorporate modern bus shelters equipped with digital technology, such as screens that forecast bus arrivals.

“It is absurd that folks do not have more convenient and attractive options,” Snyder said. “The whole corridor is underserved for transit.”

Metrobus’s Leesburg Pike Line, or 28A route, is the only service that stretches the length of the corridor, with connections to the Silver, Orange, Blue and Yellow Metro lines. A shorter, limited-stop bus route runs weekdays during only the morning and evening rush hours. Buses run about every 20 minutes on weekdays and Saturdays and less frequently on Sundays.

“If you miss your bus by a minute, you have to wait another half-hour. It can be a long commute,” said Elmer Cortez, 44, a cook who has ridden the 28A bus for eight years.

Cortez said that more frequent service would save him time and improve his commute from his Falls Church home, just off Route 7, to the Vienna restaurant where he works. Buses are rarely on time, he said, because they are often stuck in traffic. On a recent morning, he rushed to cross six lanes of traffic to catch a 10:05 a.m. bus, but that bus was 12 minutes late.

The transit systems in Arlington, Fairfax and Alexandria also serve portions of the corridor and some surrounding communities.

The historic corridor, once used by Native Americans traveling from the Potomac River to the Blue Ridge Mountains, includes booming Tysons, where planners envision a mini-city with bus service and the new Silver Line Metro as the center of the transit network. It also includes Falls Church, with its older strip malls, the diverse Bailey’s Crossroads area and historic Old Town Alexandria.

Kelley Coyner, executive director of the Northern Virginia Transportation Commission, said that improvements are planned in the next few years. The first phase of the study eliminated the most financially prohibitive options — such as adding a new Metro line or streetcar service. Now, with input from residents and other stakeholders, the commission hopes to further narrow the options, determine costs and identify funding sources. Coyner said that there is “strong commitment” by Fairfax and Arlington counties, Falls Church and Alexandria.

Several route alignments are under consideration. One of the alternatives is a bus rapid-transit (BRT) line between the Spring Hill Metro station in Tysons and the King Street station in Alexandria, with service to the Orange Line in Falls Church. Traveling the entire route would take a little over an hour, saving riders significant time, compared with the 28A bus. The service would run every 15 minutes and at least every 10 minutes during peak hours. It also would incorporate features that make BRT appealing, including use of dedicated transit lanes and an off-board payment system to allow passengers to use all doors for faster boarding.

A similar route is being studied for light rail from Tysons to the Van Dorn Street Metro station via the East Falls Church Metro station. Light-rail service could save riders time and provide more frequent service, but it also would be tougher to implement because of the right-of-way it would require — and because it is more costly.

The study, which is expected to be completed by March, would determine the availability of right-of-way. The idea probably will not be easy to sell to drivers in a corridor where the car is still king. It also presents engineering challenges because, although parts of the 13-mile stretch have three or four lanes each way, other parts narrow to two or to one lane each direction in Old Town Alexandria.

Those challenges will be addressed in the report, but they don’t take away from the existing and future needs, transit advocates say.

In a 2013 survey, 37 percent of residents in the corridor said that they use public transportation to commute to work and school, and about one-third said they take public transit for non-commuting trips.

Although the survey found that residents generally have a poor opinion of bus service in the area because of its unreliability, many said they would use transit if it improved. More than 4 in 10 of those who do not use public transportation said they would try it if it were available and convenient, with bus stops and stations closer to their homes and destinations.

Last year’s opening of the Silver Line in Tysons has provided more opportunities for improvement in the corridor, but Coyner said that the decision late last year to cancel a long-planned streetcar system in the nearby Columbia Pike corridor makes it even more important that there be quality transit service along Route 7.

By 2040, the corridor is expected to grow substantially. Population is projected to increase about 37 percent, and jobs by 42 percent, she said.

“What we want is something that is financially viable and will serve people within the next decade,”she said. “We are looking at serving people who are there now and don’t have transit, and people who are coming there.”