Mass transit benefits would exceed costs after 15 years, analysis finds

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Within about 15 years of completion, new mass transit expansion options currently undergoing public review would pay off with quantifiable public benefits that exceed the costs of building them. After 15 years, those public benefits — mainly from time and energy savings — would continue to accumulate for decades more, exceeding costs by a ratio of two to one.

These are the key findings of a benefit-cost analysis prepared for Sound Transit and released to its Board today. The Board currently is considering options for Sound Transit system expansion. Benefit-cost analysis of projects costing more than $100 million is required by the Puget Sound Regional Council as it reviews conformity with the regional transportation plan, a state mandate.

“This confirms that investing in mass transit makes sense for the bottom line," said Greg Nickels, Sound Transit Board Chair and Seattle Mayor. “By expanding Sound Transit and giving people more alternatives to sitting in traffic, we'll save both time and money."

The impacts of new transit on travel patterns in the region were assessed in five categories:

  • number of new transit riders,
  • travel time savings for new and existing travel riders,
  • savings in vehicle (highway) miles traveled due to new transit riders,
  • paid parking saved for new transit riders,
  • reduction in delay caused by traffic congestion.

Benefits-cost analysis is an economic tool used to measure the relative difference between the benefits and costs of projects or investments. Public investments generating benefit-cost ratios greater than one-to-one, or more than break even, are considered justifiable.

The study’s methodology is modeled upon state-of-the-art, conservative assumptions for U.S. transit investments. It compares expanding transit with taking no action. Anticipated regional population growth will cause significantly more congestion on existing highways by 2030. The study finds that expanding the rail system will yield significant mobility benefits, resulting in time savings of between 13 million and 34 million vehicle-hours from reduced vehicle delay per year, depending on the expansion option.

The benefit-cost analysis was prepared by Parsons Brinckerhoff for Sound Transit, and included analysis of three transit expansion options: a 20-year plan developed last year that would add more than 50 miles of light rail service to the region, and two new 12-year options adding 18 to 23 miles of light rail and increasing commuter rail service.

The Sound Transit Board is weighing these options and whether to forward one for a November 2008 public vote or wait until 2010. That decision will be made in July.


Benefit-cost studies universally rely on the concept that consumers will choose transit when the cost is less than or equal to the benefit. Consumer costs are considered in terms of both time and money.

Direct transit user benefits

After new transit investments are made, the cost of consumer travel falls – reflecting reduced overall travel time, reduced out-of-pocket costs, and/or new transit service in areas that did not previously have transit. As the cost of using transit declines and more people use transit, more opportunities for transit use become available, transit becomes more economically attractive, and the number of transit trips increases.

Indirect highway user benefits

A number of people shifting from cars to transit, and the resulting decline in highway congestion, together lower the overall cost for those who continue to travel by car. Benefits for drivers include improved travel time/mobility, savings in vehicle operating and parking costs, and reduction in highway accidents.

External/societal benefits

In addition to individual benefits, the region would benefit from fewer highway accidents and reduced air, noise and water pollution.

The full analysis is available at


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Sound Transit’s regional network of express buses, commuter rail, light rail and transit facilities connects communities in King, Pierce and Snohomish counties.