HDR taking unique approach to Tacoma Link expansion design

Written by Mischa Wanek-Libman, editor
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Sound Transit

HDR, Inc., was selected in July 2016 to provide final design services for Sound Transit's Tacoma Link Expansion and expanded maintenance facility.

HDR says the final design will be custom tailored to the unique needs of Sound Transit and the city of Tacoma, where heavy traffic means bicycles, as well as cars.

The $175-milion project will build 2.4 miles onto the 1.6-mile Tacoma Link light-rail line and will also construct an addition to the system’s existing vehicle maintenance facility in order to accommodate a new fleet of vehicles. HDR said its design would include six new transit stations and relocation of an existing terminus station. Final design is scheduled for completion by the end of 2017 with construction on track to begin in 2018.

HDR says extensive public outreach and stakeholder feedback led to the extension’s route and station selection and the company plans to continue that outreach during final design.

“Numerous special characteristics differentiate [the Tacoma Link expansion] from other lines in Sound Transit’s Link system. They include smaller scale vehicles, shared traffic lanes and simplified urban platforms,” said HDR.

HDR’s design strategy for the Tacoma Link Expansion embraces the lean project approach championed by Sound Transit. One example is the choice of a low-voltage traction power system that allows existing electrical infrastructure to power Tacoma Link vehicles, rendering unnecessary the costly installation of high-voltage infrastructure.

“We are looking at ways to simplify train control and make long-term operation more cost efficient,” said Rick Nannenga, HDR principal project manager. “This is an urban light-rail system that will operate in a public roadway, so there are a lot of different disciplines involved.”

Sound Transit’s lean approach may also lead to new GPS and “dead-reckoning” technology for vehicle detection. If adopted, this technology would make long-term operations more adaptable, cost-efficient and reliable. Tacoma Link would be among the first guided-rail transit systems to use the technology, which eliminates the need for more traditional and expensive installations and maintenance.

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