This paper gives an overview of recent practices, research and policy development within the Netherlands Ministry of Transport regarding reliability of road transport networks. A vulnerability assessment of the Netherlands national road network was performed in a few weeks time, making use of data and tools readily at hand. The study focused on discrete disturbances affecting road capacity, such as small and major accidents, road works and rainfall. The damage caused by resulting unreliability of travel time makes up a considerable part of total damage from travel delays. About half of the most vulnerable road sections are also prone to the highest total loss of vehicle-hours. It appears that densely intersected roads tend to increase vulnerability in an overloaded network. If there is one thing to be learned from this exercise, it would be that assessing vulnerability of the road network, simple though it may look, is really very complicated. Therefore, we expect that getting a good grip i.e. generally applicable for practical purposes on vulnerability of the road network and the resulting unreliability for users will take years to accomplish. As a first step we are now preparing software tools and methodologies concerning vulnerability analyses using regional transportation models, which are more detailed than the National Model System. Some of these tools have already been used, results from these studies are also presented in this paper.
Abstract