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Annual review 2022

Expanding public transit for a growing Seattle



Building on a partnership forged two decades ago on an elevated light rail project in Seattle, we are working closely with the Central Puget Sound region’s transit agency to radically expand its transportation infrastructure for a more sustainable future of community connectivity.

The economy of the US Pacific Northwest has prospered in recent decades, with some of the country’s largest companies headquartered there, including Microsoft, Amazon and Starbucks.


The economic boom has driven population expansion, with the greater Seattle area accommodating 128,000 additional residents between 2010 and 2021 − making it one of the fastest-growing cities in the US. But Seattle’s success has also brought growing pains. The subsequent rise in housing costs has driven its citizens to seek affordable accommodation further from the city centre, contributing to ever-worsening traffic congestion and pollution. And, with the population of the Central Puget Sound area expected to increase from its 2014 level of 2.9M people to a projected 3.7M by 2040, state authorities have responded by accelerating the expansion of the public transportation network.


In 1992, the Washington State Legislature authorised the creation of an agency, now known as Sound Transit, to build and operate a high-capacity transportation system connecting the urban areas of King, Pierce, and Snohomish counties. Since then, the region’s voters have approved a series of measures to fund bus, commuter rail and light rail systems through increases in local sales, property and vehicle excise taxes.


In 2008, Sound Transit 2 (ST2) approved $17.8bn of expenditure over 15 years to more than double the length of the light rail system from 32km (20 miles) to 80km (50 miles), and many of the projects funded under the measure are now close to completion. More recently, the approval in 2016 of Sound Transit 3 (ST3) allocated another $54bn, which will pay for the Central Puget Sound area network to more than double again to 187km (116 miles), with the number of stations totalling more than 80.

Existing and future network

The population of greater Seattle is expected to reach 3.7M by 2040