Recently an @sfmta_muni Twitter follower wrote, “A 3 minute ETA has somehow become 10 min and counting…” This plea for clarity and consistency is not unusual. Few things are more frustrating than waiting for a bus that doesn’t arrive when it is supposed to. The time predictions cited in that tweet are generated by a technology called NextBus. Used by transit systems around the country, and called NextMuni here, NextBus is an online tool that provides real-time transit information with vehicle arrival and departure information to customers and transit operators.
To generally answer the tweet: there are a number of reasons why vehicles may not arrive when expected. Heavy traffic, breakdowns, and other unforeseen problem can delay or completely interrupt service, which can then throw off the NextMuni predictions.
How does this affect the predictions? NextMuni uses GPS technology equipped on every Muni vehicle and advanced computer modeling to track Muni buses and trains on their routes. The technology takes into account the actual position of the transit vehicle, the intended stops and anticipated traffic patterns. So, when traffic is snarled or your bus or train has a mechanical malfunction, NextMuni predictions often become inaccurate. But you may be surprised to know that in general, the margin of error overall is less than one minute for predictions of five-minutes or less. For 10-minute predictions, the margin of error is less than two minutes.
NextMuni is a tool that is used to predict waiting times. These reported times are simply predictions meant to help riders make an informed decision on transportation options. The NextMuni system allows transit riders to obtain real-time arrival information either on their desk or on the go.
While many cool transit apps use our mapping and NextMuni data feeds to create their handy tools, you can get NextMuni updates on a smartphone without an app. NextMuni offers a great mobile version of their website. For GPS-enabled location aware phones, NextMuni will automatically show you the predictions for the nearest stops. Those who prefer to track where their bus, train, streetcar or cable car is located can watch its progress in real-time on the NextMuni map from their desktop.
By the way, our frustrated Twitter follower from the start of this story received a response from us with the location of the next bus approaching their stop. The delay in service was most likely due to traffic conditions during the morning commute. You are encouraged to be our eyes and ears on the street. Your experiences can help us make Muni better.
Information is always gladly given. For real-time service updates, follow SFMTA on Twitter @sfmta_muni, 5 a.m. to 9 p.m. Monday through Friday with scheduled alerts on the weekends, or visit us online to sign up for e-mail or text alerts sent during the same hours.
