Each bus used on a route that is included on the RTI system is equipped with automatic vehicle location (AVL) equipment that enables the bus to be tracked by global positioning satellites (GPS). The location of the bus is then transmitted to the central RTI system. In addition to the buses location, specific service information is also sent to the central RTI system either through a separate piece of equipment fitted to the bus, referred to as an on-bus unit (OBU), or the electronic ticket machine (ETM). The specific journey information received from the bus is then compared to timetable and service schedule data stored on the central RTI system. The data is then ‘matched’ and using system algorithms, journey arrival/departure times are predicted and communicated to on-street displays, web sites, Traveline (nextbuses service and SMS) etc.