Measuring Travel Time Reliability for an FCD-based Route Information System

Kurzfassung

In this paper, it is suggested to use travel time reliability (TTR) as a measure of quality of a travellers´ information service. The service in question is a route-based travel time monitoring system which is partly based on floating car data (FCD), run by German Aerospace Center (DLR). It is an integral part of a system for monitoring of natural disasters, mass events, and large traffic disasters. It has been developed at DLR during the projects DELPHI and VABENE. In contrast to many previous approaches which only used collected historical data offline, a continuous online monitoring is proposed. A related question is that for means of validating the FCD-based service by comparing its "system reliability" to the corresponding reliability performance measures for the actual traffic. Typically, such a validation would be done by field tests. In contrast, this approach aims at a continuous online-validation without the need for conducting field tests. For this purpose, the tracking data of the probe vehicles is used (i.e., an online "self-validation" is performed). Another key question is how, and to what extent, the collected historical FCD can be combined with the available current data from the probe vehicles. The gained experiences then have also been used to devise and improve the route guidance system itself.