Implementation of bus arrival prediction system is a mandate for HK franchise buses. But tons of high-rising buildings here make GPS-backbone system not as useful as we expect.
The signals cannot be sent and received from buses to satellites due to blockages of buildings & bridges. Also reflections of glass curtain wall can distort the communications.
Bus companies currently use historical data to compensate the inaccuracy mentioned above. However we cannot know how long ago the data are. Even worse the road condition always changes such that the information used can deviate a lot from actual situation. Customers are suffered and misled. The experience actually worsens especially the companies are adjusting the route frequency to adopt more and more railways around.
One of the methods can be by handshaking when buses are passing each other. If there is a GPS signal, positions and time can be dropped down. If the memory is large enough, all data collected by a bus in between the trip can be copied to another bus nearby. Once the bus arrives the terminal, the data can be uploaded and let the mainframe / cloud adjust the prediction. The data is more updated than the historical one and relevantly more accurate.