Why are real-time bus arrival times so off at my city's displays?

[PaulFA]

I’ve been trying to use my city’s new real-time passenger information displays at the bus stops, but I keep finding the predicted arrival times are way off, sometimes by ten minutes or more. It’s making me wonder if the system’s data feed is actually linked properly to the buses themselves, or if I should just go back to guessing.

[Frank11]

I use the displays at my corner stop most days and the arrival times jump around even when the bus is clearly visible on the road.

[AvaZT]

Sometimes I watch the ticker and then the bus arrives a minute later and the screen says a different time.

[Brandon44]

One time I checked the feed at a central hub and saw the next bus marked on time even though it was stuck in traffic nearby.

[EricH]

I tried setting a personal reminder and left home a bit later which helped a couple of times but not always.

[Brian81]

Could it be that the real issue is not the feed but how the stop updates the screen mid route?

[PatrickLL]

I am not sure this is the whole story maybe the display simply uses the latest known position and that can be out of date for long stops and I still end up guessing