APTA | Passenger Transport
December 21, 2009

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Sound Transitís Central Link Light Rail Line: A Major Milestone for Regional Service
BY CLIFF HENKE, Senior Analyst, Parsons Brinckerhoff, Arcadia, CA

Henke is a member of the Passenger Transport Advisory Board.

Sound Transit in Seattle achieved a major milestone this year in its development of a regional multi-modal transit system with the July opening of the Central Link Light Rail line. The line connects downtown Seattle with Tukwila, WA, 13.9 miles to the south; a 1.7-mile segment between Tukwila and Sea-Tac International Airport opened Dec. 19.

Rail was a long time in coming to Seattle—in part because of the hilly topography that makes the area so appealing. Achieving the relatively flat grade needed for a light rail system requires complex and costly tunnels as well as many stretches of aerial track. In fact, the terrain and the associated construction costs were major reasons why a rail system proposed originally in the 1960s and again in the 1970s was deferred in favor of an expanded bus system.

Although the bus system continues to serve Seattle well, buses alone will not be enough to handle the growing travel demand in the region. With the city’s already dense development constrained by hills and surrounding bays, lakes, and waterways, not enough space is available for wider roadways.

“Leaders in the region have long been convinced that expanding transportation capacity and maintaining Seattle’s livability requires an investment in grade-separated rail, as well as expanding and interconnecting the other modes of public transit: vanpools, city bus, regional bus, commuter rail, streetcars, and ferries,” said Jared Smith, principal-in-charge for Parsons Brinckerhoff (PB), which has been supporting the development of transit in Seattle since the 1970s in a range of planning, design, and construction management roles.

Central Link is the first segment of a planned 55-mile regional light rail system that will serve King, Pierce, and Snohomish counties—part of the largest transportation project undertaken in the history of Washington State. It created thousands of jobs for the Puget Sound region and its construction involved approximately eight million craft-labor hours.

The 13.9-mile Central Link route contains 12 stations and offers a fast, reliable alternative for commuting and intra-city travel. The project is the result of more than a decade of planning and negotiation among local, state, and federal transportation agencies, as well as engineering and construction innovation and effort.

It is a key component of Sound Transit’s high-capacity transit system, which is expected to carry more than 128,000 passengers by the year 2020 and help meet the transportation needs of the growing region.

The technical challenges of this large-scale, complex project ranged from the record-setting Beacon Hill Station, built 165 feet below surface—the deepest constructed in soft soils in the U.S.—to the innovative 4.3-mile-long aerial light rail guideway of the Tukwila segment. The work performed for both the Tukwila elevated structure and the Beacon Hill Station represents significant advances in engineering and construction techniques and methodology.

Until Dec. 19, the alignment ran from downtown Seattle south to a temporary terminus at International Boulevard in Tukwila. With the opening of the new Airport Station on Dec. 19, the line provides a direct route to Sea-Tac International Airport. Future planned extensions will create a regional light rail system that will run north to Lynnwood/Snohomish County, east to Redmond’s Overlake area (adjacent to the Microsoft campus), and south to the Federal Way area.

The Bigger Picture
In November 2008, voters approved a $17.8 billion (in year of expenditure) regional transit system plan that will add another 36 miles of light rail over the next 15 years, along with bus and commuter rail improvements. The expansion, known as Sound Transit 2 (ST2), will more than triple ridership.

ST2 also calls for substantial enhancement of commuter rail service and capacity and a 17 percent increase in bus service levels.

“Voters demonstrated their support for transit by approving a 0.5 percent sales tax to fund the next phase of the system expansion,” noted Smith. “The challenge now is to integrate modes effectively, foster communication among transit providers, and maintain the system’s flexibility into the future.”

At the heart of the plan is the intention to complement regional growth and to improve transit connections between regional centers—such as Bellevue, Tacoma, downtown Seattle, the University of Washington, and the airport—thereby reducing the need for the automobile and dramatically improving mobility for the region’s residents. Construction on the University Link, a three-mile light rail extension that will connect Seattle’s central business district with the University of Washington to the north, began in March 2009.

So far the development of a new transit system in Seattle has been a resounding success. “Enthusiastic crowds boarded trains throughout the Central Link’s opening weekend, and since then ridership has been consistent with projections,” said Smith. “Seattle is serving as a shining example of the axiom ‘if you build it they will come’ and will continue to do so well into the future.”

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