I got to ride the Metro a couple of weeks ago. This was not a planned trip, but I boarded willingly due to car trouble and my desire to get back on the horse after my Covid-19 vaccination.
When I boarded at the NIH Metro stop, the station and cars were nearly empty. I headed off to Van Ness with four others – all of us in masks – in my car.
I’ve been curious about air flow and filtering on the Metro trains and Metrobus, and had been planning to look up the information before I took the plunge. After my unplanned ride, I checked wmata.com and found no direct links to Covid updates on the front page. Using the search term “Covid” brought up this page: “a continually updated snapshot of case numbers” and ridership data. The page mentions efforts to sanitize surfaces, but nothing about the air.
Why does this matter? Telling people about air filtration could help Metro entice riders to return.
After checking with contacts at WMATA and ANC 3F, I got an email response from Sherri Ly in WMATA media relations. And she gave me the scoop about the air.
On Metrorail cars: Metro uses MERV-7 filters and the air is exchanged every three minutes. (Here is a chart of filters and the size of the particles they capture.) These filters will not catch Covid particles, which are 70-90 nanometres or .07-.09 microns. WMATA is planning to begin a pilot project using ultraviolet technology and MERV-13 filters – which are used in the station air filtration systems and do filter out the virus. Ly said testing and evaluation are expected to take eight months.
On Metrobuses: The filtration systems have been upgraded across the fleet, though Ly did not provide specific information about filters. Ly also told me that air is exchanged on 40- to 60-foot buses every two to three minutes. Plus, the outside air is exchanged every time the buses open their doors, which happens quite frequently. The opening and closing of Metro car doors also impact air exchange.
In December, Metro introduced a tool for tracking crowding on buses in real time “made possible by technology aboard every bus that senses when customers enter and exit.”
The data is at buseta.metro.com and on transit apps that use the WMATA data.
Metro cars do not have the same sensor technology, but WMATA said it would make crowding predictions available based on recent data.
Are you riding the bus or rail? What has your experience been like?