A passenger information [display] system (PIS or PIDS) is an electronic information system which provides real-time passenger information. It may include both predictions about arrival and departure times, as well as information about the nature and causes of disruptions. It may be used both physically within a transportation hub and remotely using a web browser or mobile device. Current operational information on service running is collected from automatic vehicle location systems and from control systems, including incident capture systems. This information can be compared by computers with the published service timetable to generate a prediction of how services will run in the next few minutes to hours.

This may be informed by additional information: for instance, bus services will be affected by congestion on the road network, while all services may be affected by adverse weather conditions.

The capital and revenue costs for traveller information systems can be calculated with reasonable accuracy. However, the derivation of tangible financial benefits is far more difficult to establish and as a consequence, there is very little research. This directs the business model for information systems towards the "softer" merits such as traveller confidence etc. It is worth noting that there must be an actual value as individuals are willing to pay for systems that give them access to real time data relating to their journey. The difficulty is establishing what this is for each individual person and perhaps each individual piece of roadside hardware.