this app is (often) accurate nice design - has a very simple interface, uncluttered, no spam, no ads, and tells you a valuable piece of info: how much time you have to make the next train. sounds great, right?
two problems:
1. sometimes (roughly 20% of the time the app is significantly inaccurate). maybe sometimes it can’t get train location data from the MBTA and falls back to using schedule data - i don’t know. but as a user, you have no way to tell (through the simple interface) whether it the app is going to be scary-accurate (where it tells you within 5 seconds of when the doors on the train are closing) or randomly inaccurate. it would be much better for me if the app could say “i don’t know” or flag the times as “best guess” or whatever in situations where it can’t get up-to-date data - just giving bad estimates undermines confidence and makes the app much less useful overall.
2. it doesn’t work well at end-of-line stops (like Alewife, in my case) where the train departure seems to depend on semi-random variables like how long the conductor takes to walk from one end of the train to the other, or how long it takes for someone to come back from bathroom break or whatever (vs. just interpolating arrival time from when the train passes the previous stop). so the app doesn’t really inspire much confidence in predicting alewife departures.
my comments are based on using this app on the red line - performance may be different for other lines.