The MBTA is sharing crowding information during the pandemic. So, how does it work?

The latest MBTA digital feature would have been nice to have months ago, but now seems borderline critical during an infectious disease outbreak: live information on how crowded that next bus is, allowing riders to decide if there’s enough room to safely board and observe social distancing.

As part of the live tracking service in the popular smartphone app Transit, and on the T’s website as well, riders can now see one of three labels alongside bus locations: “not crowded,” “some crowding,” or “crowded.” The feature is limited, for now, to just 16 bus routes, with more expected over the summer, and is based on technology that automatically counts passengers as they board and unload.

I conducted a test-run of the service using the Transit app one morning this past week, boarding the 110 bus at its starting point in Wellington and charting how the messaging changed as riders boarded and unloaded through Everett and Revere toward Wonderland.

Most riders probably won’t use the feature this way. The idea isn’t to monitor crowding once you’re already on the bus, but to gauge crowds as you plan your trip, possibly shifting your travel time if a bus looks worryingly full. This way, though, allowed me to compare the app’s read of the 110 capacity with what I could see first-hand.

The system seemed to work basically as advertised. As people boarded and unloaded, the status of the 110 shifted occasionally. The ride lent some insight into when buses are considered to have reached a certain point of crowding, and how quickly that information gets to riders.

During the pandemic, the T has said 40-foot buses, such as those on the 110, are considered crowded at 20 passengers, giving each rider about a meter of space — less than the commonly recommended six feet. Sixty-foot buses are considered crowded at 31 people.

Crowding information is now displayed for some bus routes on the MBTA's website and the smartphone app Transit.

My trip began as “not crowded,” as there were just seven passengers aboard. After a few stops, we’d accumulated a few more riders — nine in total, plus the driver. That was enough for the status to move to “some crowding.” It toggled back down to “not crowded” a few stops later after one rider left.

There appeared to be a small lag between the time passengers boarded and when the app adjusted the bus’s status. At one point, after a busy stop, we had 11 riders aboard, but the app still said “not crowded.” It adjusted after a short moment, and the MBTA confirmed the vehicle must travel 200 feet before the real-time info is updated.

The T also said it shifts from the “not crowded” to “some crowding” language at 10 riders on a 40-foot bus, so it was not clear why it also adjudged nine passengers as “some crowding.” I never saw the bus get to the point of being “crowded,” which would have happened at 20 riders, according to the MBTA. I did check the app later in the day and saw some buses had crossed into “crowded” territory.

Back before the virus, the T considered a rush-hour bus to be overcrowded at 56 riders, so the 20-rider threshold is a marked change. The T is not, however, kicking riders off or preventing them from boarding once that threshold is met, but instead will rush extra buses into service to try keeping levels down. The agency is also assuming ridership will remain low for many months, though buses have had a higher rate of riders stick around throughout the pandemic than trains.

Maybe it’s the heightened awareness from the pandemic, but overcrowding is now a much more relative measure; that is, it’s surprising how much more crowded a bus feels with 11 riders than nine. Six months ago most riders would have rejoiced at that level.

After getting off the 110 at the end of my trip — it was decidedly “not crowded” — I asked other riders at the terminal what they thought. How many fellow passengers is too many?

Drine Barze of Malden pegged it at five to 10 riders. She’s been taking the bus several times a week during the pandemic and said they rarely exceed that level.

Another passenger, who declined to give her name, said she feels fine until a bus gets more than 12 riders. But she suggested there’d be room for more if the T wasn’t blocking off the front of vehicles to separate riders from drivers. “We have to pass close to all the people,” she said.

When might the feature roll out across the entire bus system? Officials said they must first test the accuracy of the live counts on each new bus route. Not only is it a time-consuming process, but there have indeed been glitches in tests on some routes, delaying the rollout on popular lines such the 111. The problem may be a connectivity issue along these routes, making it difficult to communicate the data in real time; the MBTA said its contractors have promised a “quick fix.”

And for now, at least, this system is only on buses, not commuter rail and subway trains, because those vehicles aren’t equipped with the same passenger-counting technology. The T has said it may be able to share crowding information for trains eventually, but it will instead be based on ridership trends from prior days and not real-time information.