Bus passengers are very interested in knowing whether or not the bus that they are expecting will turn up on time, or even turn up at all, and real time information systems on apps and at bus stops are supposed to provide that information and reassurance.
And passengers paying for their fares using tap on/tap off want to be assured that they will be charged the correct fare for their journey and that, if daily or weekly capping applies to their journeys, that those caps will be made correctly.
Both of the above require complex IT systems on the buses, in the offices of bus companies, and in the financial services industries, to make sure that they work properly. Whilst most passengers will not be particularly interested in how the systems work - they just want to know that they do work - some may be interested in learning more about the minutiae of the processes involved. If that is you, please take a look at a couple of guides that are available online.
Tracking of buses in real time is dependent on something known as Bus Open Data Service, BODS for short. Roger French who writes the very readable Bus and Train User blog has covered the subject in a recent blog. He explains, for example, why sometimes one information source such as a bus operator app will show the position of a bus differently from that shown on another source such as bustimes.org.
How tapping on and off a bus results in the correct amount being charged to the bus passenger’s bank account is covered in great detail in a booklet written by the CEO of Littlepay and can be downloaded from Fundamentals of Transit Payments. Littlepay is the company that runs the payment system behind tap on/tap off on Go Cornwall Bus and First Bus vehicles in Cornwall. Whilst Littlepay obviously has a vested interest in promoting their particular payment solution and their company, it is a very instructive read in how tapping on to a bus in the middle of nowhere in Cornwall results in the correct fare being taken from your bank account a matter of minutes, if not seconds, later. For example, it explains how when you tap on a card reader in a shop, the reader can, within a few seconds, check with your bank that you have sufficient funds to pay for the transaction, and, therefore whether to allow the transaction to proceed; but when getting on a bus, a delay of a few seconds would be unacceptable. Instead, the ticket machine has to make a decision within a target time of 0.3 seconds as to whether or not to accept your card. The Littlepay book explains how it does it.