Matt L wrote:The same person who told me about the rail system real time feeds also told me that the bus system doesn't actually use GPS, it uses a system called geo-fencing which basically is sensors in traffic lights that detect when buses go past them which feeds the information back to make a guess as to where the bus is at any given time.
Was this a reliable source?
The bus driver display for lateness clearly has a GPS status LED.
Back in the 1990s, there was a sensor-based system along Dominion Road, but that was pulled out many years ago now. I remember it from my school-age days, there were displays at the Balmoral and Valley Rd shops.
geoff_184 wrote:I'm thinking mainly of all those bus stop display signs, all of which show Britomart departure data only. For example if a bus departs Britomart 10 minutes late, the real time info at all the bus stops along the route have 10 minutes manually added regardless of where the bus actually is. It's not real time info at all.
Case in point, the 136 bus departed Henderson three Sundays ago while the sign was still saying it was 6 minutes away.
I'm pretty sure that's not right either.
This is my understanding of how it works:
When a bus has correctly logged on to the GPS tracking system AND has departed its starting point, it is GPS-tracked in real-time with predicted arrival times calculated for stops ahead of it.
HOWEVER, if one of those two prerequisites it not met, all the signs (which includes online and mobile displays) instead show an estimated arrival time based off the timetable.
The problem with this current system is there is no way to tell from the waiting passenger's point of view which of these two systems is calculating the arrival time shown. Clues that actual real time data is used is if the shown ETA counts down unevenly or even goes up - this shows something is being recalculated from something that is varying (ie, the actual position of the bus).
I have noticed that the GPS arrival accuracy of the inbound buses my wife and I use has improved as newer buses have been used on Sandringham Rd services.
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