Study Recommends New Mezzanine to Connect Red/Purple at Silver Spring
To handle future ridership demand, Silver Spring may need a new mezzanine to connect Metrorail to the planned Purple Line light rail station.
Last year, we began a study looking at potential station capacity issues at Silver Spring. The assessment determined that the demand at the Silver Spring Metrorail station (entries and exits) is adequately served by the existing station infrastructure. Since then, the study has assessed the future conditions that will be impacted both by ridership growth due to growth of jobs and households in the station area, but also the arrival of the Purple Line light rail to Silver Spring.
The Purple Line station at Silver Spring is planned as an elevated platform and mezzanine, with the mezzanine connecting to the top floor of Silver Spring Transit Center, Metropolitan Branch Trail, and Ripley Street to the south. The elevated light rail platform will be approximately 80 feet above the street, about the height of the current MARC pedestrian bridge. The MTA design team envisioned a possible direct connection between Metrorail and the Purple Line, as illustrated in the red shape in the center of the above image. Without such a connection, riders transferring between Metrorail and the Purple Line at Silver Spring would have to descend those 80 feet to the ground level, enter an existing Metrorail mezzanine, and then ascend again to the Red Line platform.
One purpose of our study was to evaluate the demand for such a direct connection and assess the benefits. The analysis found that by 2030, the ridership growth (due to growth of jobs and population in the station area) paired with additional demand due to the Purple Line would result in crowding on the Metrorail platform, the Metrorail mezzanine and on the Purple Line mezzanine, as illustrated in the cumulative density maps below. The analysis predicted that over 50% of customers using the Purple Line mezzanine would experience crowded conditions. And without a direct connection, a customer’s transfer time between Metro and the Purple Line would exceed three and a half minutes.
The study developed a design proposal for a new direct connection from the Purple Line mezzanine to the Red Line platform. This connection would take the form of a new Metrorail mezzanine above the south end of the station that included three escalators, one staircase, and a pair of elevators. This design would eliminate nearly all of the crowding concerns, reducing the percentage of Purple Line customers experiencing crowded conditions to 11% or less, and reducing the transfer time from three and a half minutes to under 90 seconds. These time savings will add up: The study estimated approximately 10,000 peak-period transfers per day between Purple and Red in 2020, and the improvements proposed would save these riders over 200,000 hours per year. Time is money, after all, and when you add this up, riders will save nearly $7 million in monetized time savings each year. That’s hundreds of dollars saved by each rider each and every year.*
In fact, the model predicts that, once built, the new mezzanine will be the most-used entrance to the Silver Spring Metrorail station.
The video below shows a simulation of the proposed direct mezzanine connection.
The Metro study team has been working closely with the Purple Line planners to ensure compatibility between designs, and we have submitted the preliminary design drawings for incorporation into the evolving plans for the Purple Line’s Silver Spring station. Metro is currently working with Montgomery County to identify potential sources of funding for the construction of this important public transportation infrastructure project.
The final report is published here and on wmata.com.
* Note on time monetization: Per USDOT guidance, Metro uses one-half the average hourly wage rate for calculating in-vehicle travel time cost savings. For the Washington region, this value is $17. Metro applies a factor of two to the in-vehicle travel time for reflect the perception that transit access/transfer time is at least twice as onerous than in-vehicle travel time.