jm + bristol   1

The curious case of disappearing buses
Nice investigation into some dodgy pseudo-real-time bus location data in the Bristol real time passenger information system (via Tony Finch)
So what have we learned? One thing we are sure is that data of different qualities – genuinely real-time, pseudo real-time (Type 2 and Type 1), and non-real-time (scheduled) data – all present in the data stream.

Among these the most interesting are Type 2 pseudo real-time data. They appear to be the root cause of the phenomenon of disappearing buses.

Type 2 pseudo-real-time data are not totally bogus. One possible explanation of their existence can be this. The bus company has limited but not full tracking information on some of their buses. For example, it may know the location of a bus only when the bus leaves the bus terminal. Instead of not showing any data at all about the bus, the bus company uses interpolation to predict the locations of the bus, and reports these as if those are real-time data.
via:fanf  bristol  buses  public-transport  rtpi  estimation  open-data 
5 weeks ago by jm

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