With increasing demands for better and reliable service due to improvements in the quality of life, many systems (such as the communication networks and drainage systems) have incorporated "reliability analysis" as an integral part in their planning, design and operation. However, very little attention has been given to the reliability analysis of road networks. On the other hand, Intelligent Transport System (ITS) has developed rapidly in recent years. Impetus was received from the investigation of the effects of ITS on two types of road congestion; namely, recurrent and non-recurrent congestion. The former is referred to as the predictable traffic conditions caused by an excess of demand over supply, following a defined pattern, e.g. peak period traffic and seasonal variations. The latter includes non-recurrent congestion situations resulting from a temporary reduction in the capacity of a length of road due to accidents, bad weather, construction works or other short-term disruptions to traffic flow. The introduction of ITS and the concept of "reliability analysis" has generated an urgent need for better understanding of road network reliability under recurrent and nonrecurrent congestion scenarios.
In the International Workshop on Network Reliability and Transport Modelling, held in Hong Kong in December 1998, experts from Australia, Canada, Hong Kong, Japan and UK have presented papers on network reliability and transport modelling. Among them, a number of papers are focused on the subject of road network reliability which is of particular interest to practicing engineers and researchers involved in transport network design and analysis. These papers are worthy of further elaboration and expansion. This Special Issue is devoted to the subject of network reliability and to provide a broader platform for dissemination of the research findings by these authors. In total, eight papers are included in this issue and they are presented as follows.