Park & Ride Historical Background

This page serves to provide background on the Sound Transit Park & Ride. The information contained within has not been updated.

In 1996, Mercer Island voters supported Sound Move, a regional transportation plan that created Sound Transit’s Regional Express Bus service. Sound Transit’s project proposed adding 230 spaces on Mercer Island as part of a trio of I-90 related improvements on the Island.

Sound Transit has worked through the I-90 Project Steering Committee to identify a preferred location for a park-and-ride facility they will build on the island. The Mercer Island City Council recommended the south of I-90 underground facility as its preferred park-and-ride location in November of 1999, which recommendation was supported by the Steering Committee.  The estimated cost of that alternative, $13.8 million for one floor of parking and $22 million for two floors, significantly exceeded the project budget of $13.3 million.

Up until January of 2001, Sound Transit treated the I-90 roadway improvements, park-and-ride, and transit station as a combined project. However, decision-making on an I-90 Center Roadway configuration has proven complex and time-consuming. In an effort to advance a park-and-ride solution, in December the City Council asked Sound Transit to “decouple” the park-and-ride and transit station parts of the project from the decision on the I-90 roadway configuration. Sound Transit agreed to do so.

In January 2001 Sound Transit summarized the estimated costs for an underground parking structure at the preferred location and concluded “(T)he project budget cannot support a project like this.” At the same time, the letter restates Sound Transit’s commitment to building additional park-and-ride spaces on Mercer Island, and the intent to work with the City to “explore alternatives.”

In March of 2001, the Council directed the City Manager to explore the possibility of other options, specifically the opportunity to develop some sort of public-private partnership with new developments planned in the Town Center. Staff was asked to look into whether additional public parking for Mercer Island residents could be added to the Island Market Square property project at approximately SE 27th Street and 78th Avenue SE and/or to the project planned for the property at approximately SE 27th Street and 77th Avenue SE. 

In summer 2002, a private developer, Dollar Development, proposed an option in which they would construct an additional 200 parking spaces to be used as park and ride spaces.  Sound Transit staff worked with the developer to evaluate this option.

In September 2002, the Sound Transit Executive Committee directed staff to continue developing the Dollar Development option and to build cost information for comparison purposes.

Sound Transit’s preliminary analysis by geo-technical, structural, transportation and parking design consultants compared the advantages, disadvantages and the cost of constructing 200 park and ride spaces at the proposed development with the cost of constructing 200 underground spaces and with adding 400 above-ground spaces at the existing Mercer Island park-and-ride lot located on North Mercer Way.  The analysis found that:

• Dollar Development’s current design of the park and ride spaces is tight and has reduced maneuverability.  Redesign may be required to meet Sound Transit’s circulation requirements.  There may be a cost impact.
• Dollar Development’s design would locate Sound Transit park and ride spaces on two separate floors, about 1200 feet from the existing transit center.
• Access control to prevent use of park and ride spaces by non-transit users has not been addressed in the design concept.
• Structurally Dollar Development’s design can be modified to accommodate an additional floor of parking.
• Adding 200 trips to the traffic analysis for this site is not a fatal flaw.  The environmental analysis (SEPA) for the site would need to be amended.
• Per stall costs for the proposed Dollar Development option and an underground parking option at the existing site are similar.  However, Sound Transit policy rules out the incrementally higher cost of underground parking spaces at any park-and-ride lot it is constructing.
• The per stall cost of two floors of above-ground parking at the existing site is still the most cost-effective option of providing more park and ride spaces on Mercer Island however, Mercer Island staff and council are opposed to this option.

The proposed concept had potential benefits to Sound Transit and Mercer Island.  It was hoped that it would provide an opportunity to meet Mercer Island’s park-and-ride needs at a potentially reasonable cost.  The site would require a longer walk to access transit service, but it is within industry standards for acceptable walking distances to transit.  Sound Transit staff has identified functional requirements for the park and ride spaces including location of spaces at street level closest to bus access, consistency with Sound Transit and ADA design standards, access control, security, maintenance and hours of operation.  Sound Transit would acquire the park and ride spaces through a condominium type arrangement which would include some property rights and control in the facility.  The arrangement would be structured as a turn-key agreement in which Sound Transit would set forth specific requirements and Dollar Development would commit to providing them for a maximum price, with a defined schedule.

Sound Transit staff updated their Executive Committee on the status of negotiations in December, 2002.  There was an inability to close the gap between the $26,500 per parking stall cost identified by Dollar Development and the $19,000 per stall cost set by Sound Transit. 

Consequently, this public/private development option was abandoned.

As part of their preliminary design efforts, Sound Transit collected the following data to assist with interim parking and transit operations during reconstruction of the park-and-ride lot.  To accommodate the number of Mercer Island transit riders during closure of the existing lot, Sound Transit plans to lease additional park-and-ride spaces south of I-90. Sound Transit also collected numerous comments and suggestions. 

Existing Use of Mercer Island Park-and-Ride and Bus Stop (2002)

The number of boardings is more than 3 times the number of available parking spaces, suggesting that a large number of transit riders are walking to the transit stop, being dropped off, or parking elsewhere on the Island, in addition to a small number of transfers.

Table 2 provides information on the origin of the users of the Mercer Island Park-and-Ride, based on license plate information. [See below for 2015 user data based on license plate surveys.]

Table 2: Origin of Users of Mercer Island Park & Ride (2002)