By Joe Fitzgerald Rodriguez : sfexaminer – excerpt – (animation)
Most Muni riders at one time or another have shared the experience of standing at a bus stop and glancing at the LED sign which predicts the next bus.
Mysteriously, the sign stays stuck on the same prediction for minutes at a time — a common occurrence, according to transit app company Swyft.
NextBus predictions can be inaccurate 40 percent of the time if a bus is 20 minutes or more away, according to a Swyft study, released Thursday. “NextBus accuracy plummets as it tries to predict arrivals further out in time,” Swyft wrote in a summary of its study findings.
NextBus sent the following statement in response to the study: “In urban environments the time between buses may only be 8 to 20 minutes, so people aren’t looking out 30 minutes for a bus. They want to see the next one or two.”…
Smartphone app makers like Swyft, Metro San Francisco, Routesy, Pocket Muni and others use the data as the backbone for their bus prediction services…
The SFMTA has a similar service for its riders, but it sends Twitter, email and text message announcements of delays to users…
And as for inaccurate predictions, SFMTA wrote that GPS technology aboard buses “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.”
So for instance, if a vehicle is two blocks away from your stop but stuck in traffic, it may read “2 Minutes” away until the bus is able to move – no matter how long it takes.
In that way, the “time” predicted is perhaps, more accurately, a measurement of distance… (more)