Sound Transit 2
Sound Transit 2

Frequently Asked Questions

  1. Why is light rail planned for I-90? Why not just wait and put it across SR 520 when that bridge gets rebuilt?
  2. Will light rail on I-90 make traffic worse?
  3. Can trains operate safely on a floating bridge?

Answers

Answers to Frequently Asked Questions

  1. Why is light rail planned for I-90? Why not just wait and put it across SR 520 when that bridge gets rebuilt?
    • Light rail can be quickly and cost-effectively built on I-90. This has been the plan for over 30 years and it still makes the most sense today. The I-90 center roadway was designed to accommodate light rail.
    • 1976 Memorandum Agreement for I-90 was signed by the cities of Seattle, Bellevue and Mercer Island, King County, Metro Transit and the State Highway Commission. It directed that bridge design and construction accommodate future conversion to rail and commits the two-lane center roadway for that purpose.
    • In a 2004 Amendment, the parties agreed that I-90's ultimate configuration would be high-capacity transit in the center roadway and HOV lanes on the outer roadway and directed action to implement this as soon as possible.
    • I-90 better connects Bellevue and Seattle, the two biggest economic engines of the region.
    • In its 2002 Trans-Lake Project, WSDOT affirmed that I-90 makes the most sense for the first high-capacity transit service across Lake Washington because it will pass through Bellevue without an extensive detour, be finished sooner and could cost less than similar service in the SR 520 corridor. The study recommended consideration of future high-capacity transit on SR 520.
    • There are insurmountable technical and financial challenges to putting the region's first cross-lake rail connection on SR-520. For more information. insert link to I-90 fact sheet (also include on resource page)
    • The Mass Transit Expansion plan includes funding to implement bus rapid transit service on SR-520, and funding to study the possibility of adding future rail service on the corridor.
  2. Will light rail on I-90 make traffic worse?

    • Light rail offers more than 50 percent greater people-carrying capacity than the current I-90 center lanes, with the ability to serve up to 12,000 people per hour in each direction.
    • The corridor will have the same number (eight) of general purpose lanes as today. New 24-hour HOV lanes in both directions will replace the express lanes that currently operate only in the peak direction (westbound in the morning, eastbound in the afternoon).
    • A WSDOT study found that with light rail on I-90, traffic flow will be better for most commuters in most directions during most times of the day. It also found some times when the projected traffic flow would be slightly impacted by removal of the reversible lanes.
      • It is important to note that WSDOT's study did not take into account any potential mitigation measures. More detailed traffic studies are currently underway as part of the East Link Environmental Impact Statement.
    • The new configuration recognizes that nearly half (45 percent) of the trips across the I-90 bridge are now in the off-peak direction (to the Eastside in the morning, for example).
      • Freight traffic on I-90 is heavier in the reverse-peak direction, heading eastbound in the morning as freight leaves the Port of Seattle and westbound in the afternoon as freight arrives.
    • Even with the worst-case analysis, the traffic study showed significant benefits, including reduced weaving across the bridge and increased capacity in the reverse peak direction.

  3. Can trains operate safely on a floating bridge?

    • Extensive engineering work shows that light rail trains can operate safely on a floating bridge. Rail systems operate successfully on suspension bridges that experience greater movement than the I-90 floating bridge.
    • Two different independent panels of experts looked at the feasibility of adding light rail to the bridge. Neither found it could not be done.
    • A load test conducted by WSDOT in September 2005 simulated light rail train operation on the I-90 bridge. It affirmed 2001 computer modeling work and structural analyses demonstrating that the bridge is capable of accommodating light rail operation.
    • The bridge can be structurally retrofitted to accommodate the addition of light rail to general purpose traffic on the I-90 roadway.
    • Rail is successfully operating on aerial bridges in Vancouver and Lisbon that have similar or greater degrees of movement.