With infill stations, older transit agencies extend their reach

» A new station on Boston’s Orange Line prepares for opening, but infill stations of its type are all too rare.

Want to know a secret? One of the best ways to increase transit ridership at a reasonable price requires little additional service. It requires no new line extensions. And it can be done to maximize the value of existing urban neighborhoods.

This magic solution comes in the form of the infill station–a new stop constructed along an existing line, between two existing stations. Next week, Boston’s MBTA transit agency plans to open a new stop, Assembly Station, along the Orange Line in Somerville, a dense inner-ring suburb just to the northwest of downtown Boston.

Assembly is the latest in a series of recent infill stations in the U.S. located along older heavy rail lines whose other stations were generally constructed decades ago. Washington, D.C.’s NoMa Metro Station opened in 2004; the San Francisco region’s West Dublin/Pleasanton BART Station followed in 2011. In Boston, new stations have been constructed along the upgraded commuter rail-becoming-regional rail Fairmount Corridor. And Chicago has had success with the opening of two infill stations in 2012, the Morgan Station in the city’s West Loop and the Oakton-Skokie Station in the northern suburbs.

Yet those expansions are exceptions to the rule. Two infill stations are currently planned in Northern Virginia, at Potomac Yard along the Metro in Alexandria and at Potomac Shores along the VRE commuter line, and one new station is under construction along the Green Line in Chicago.

But few other cities or transit systems are even considering the possibility of investing in infill stops, even as line extensions are proliferating around the country. That’s a big disappointment.

The advantages of infill stations result from the fact that people are simply more likely to use transit when they’re closer to it — and from the fact that the older transit systems in many cities have widely spaced stations that are underserving potentially significant markets. Erick Guerra and Robert Cervero, affiliated with the University of California-Berkeley, have demonstrated that people living or working within a quarter mile of a transit station produce about twice as many transit rides as people living or working more than half a mile away. In other words, with fewer stations on a line, the number of people willing to use public transportation as a whole is likely reduced.

Assembly Station, which has been in the works for several years, promises significant benefits — 5,000 future daily riders taking advantage of a 10-minute ride to the region’s central business district, at a construction cost of about $30 million. The station fits in the 1.3-mile gap between two existing stations and is the first new stop built along Boston’s T rapid transit network in 26 years. When combined with the $1.7 billion Green Line light rail extension planned for opening later this decade, 85 percent of Somerville’s residents will live within walking distance of rapid transit, up from just 15 percent today.

The cost-per-rider comparison between the two Somerville projects is indicative of the value offered by infill stations: While Assembly Station cost about $6,000 per rider served, the Green Line Extension will cost $38,000 per rider served — six times more. Both projects will provide benefits, but the cost-effectiveness of infill stations in terms of attracting riders is clear. While infill stations will reduce transit speeds to some extent, within reason the number of new riders they attract will more than make up for the change.

Assembly Station was made possible in part thanks to a $15 million contribution from Federal Realty Investment Trust, which is building a $1.5 billion mixed-use community adjacent to the station. This Assembly Row project will eventually include 2,100 housing units, 500,000 square feet of retail, and 1.75 million square feet of office space, in effect creating a transit-oriented mini-city in an area that was once home to an automobile plant and, after that, a strip mall.

The ingenious decision to combine the creation of a dense new development with a new transit station encourages the production of a virtuous cycle of more people living near transit who thus are more likely to use transit.

There are many other places throughout the country where there are similar opportunities for new infill stations. San Francisco’s BART studied a new subway station at 30th Street and the Mission years ago but has done little to act on the idea. Other cities have the physical conditions that are right for infill stations but little momentum to implement them. Portland’s light rail system, for example, has several long inter-station gaps: The distance between Lloyd Center and Hollywood/NE 42nd (east of downtown) is 1.7 miles, certainly long enough to justify a new station in between. In Atlanta, similarly, the gap between Arts Center and Lindbergh Center on the Red and Gold Marta lines is 2.7 miles, passing through a zone of potential redevelopment.

These examples are just the tip of the iceberg; there are dozens of similar situations around the country.

Transit agencies looking for ways to maximize the use of their existing lines should look to literally fill the gaps between their existing stations. In doing so, they offer the opportunity to build additional ridership and spur redevelopment.

Image at top from MBTA.