Road Network Vulnerability Research Articles

User inequity implications of road network vulnerability

An important purpose of the road transport system is to allow people to commute in efficient and reliable ways. For various undesired reasons, however, link capacities are sometimes reduced or links are closed completely. To assess and reduce the risk of such events, a key issue is to identify road links that are particularly important, i.e. roads where disruptions would have particularly severe consequences. This paper presents a method for incorporating user equity considerations into a road link importance measure. As a complement to measuring the total increase in vehicle travel time, we also measure the disparity in the distribution among individual users. These two components are combined to form an equity-weighted importance measure. We study the properties of this measure both analytically and in a full-scale case study of the Swedish road network. A main result is that increasing the weight put on the equity aspect transfers importance from the main roads to smaller local roads. The use of the measure in transport policy and planning is discussed.

Road network vulnerability–evaluation of measures in ranking damages and developments

In this article a practical example on studying vulnerability using the method of the critical scenario and multi-criteria analysis is presented. Giving a simple method to handle reliability related to a certain path, section, link, junction or a whole trip for travelers and operators of urban road networks as users of traffic information systems it would be a huge step forward. The best would be to have one single parameter coming from an engineering calculation or a model, which would mean the same for the user and the engineer, and both of them would be able to use it as it was. Introducing a clear definition of reliability and vulnerability of road networks used by a wide range of applications is of capital importance. This article makes some steps towards achieving this goal.

Network structure and travel patterns: explaining the geographical disparities of road network vulnerability

Inevitably, links in the road network are sometimes disrupted because of adverse weather, technical failures or major accidents. Link closures may have different economic and societal consequences depending on in which regions they occur (regional importance), and users may be affected differently depending on where they travel (regional exposure). In this paper we investigate in what way these geographical disparities depend on the road network structure and travel patterns. We propose aggregate supply-side (link redundancy, network scale, road density, population density) and demand-side (user travel time, traffic load) indicators and combine them in statistical regression models. Using the Swedish road network as a case study, we find that regional importance is largely determined by the network structure and the average traffic load in the region, whereas regional exposure is largely determined by the network structure and the average user travel time. Our findings show that the long-term vulnerability disparities stem from fundamental properties of the transport system and the population densities. Quantitatively, they show how vulnerability depends on different variables, which is of interest for robust network design.

Attacker–defender models and road network vulnerability

The reliability of road networks depends directly on their vulnerability to disruptive incidents, ranging in severity from minor disruptions to terrorist attacks. This paper presents a game theoretic approach to the analysis of road network vulnerability. The approach posits predefined disruption, attack or failure scenarios and then considers how to use the road network so as to minimize the maximum expected loss in the event of one of these scenarios coming to fruition. A mixed route strategy is adopted, meaning that the use of the road network is determined by the worst scenario probabilities. This is equivalent to risk-averse route choice. A solution algorithm suitable for use with standard traffic assignment software is presented, thereby enabling the use of electronic road navigation networks. A variant of this algorithm suitable for risk-averse assignment is developed. A numerical example relating to the central London road network is presented. The results highlight points of vulnerability in the road network. Applications of this form of network vulnerability analysis together with improved solution methods are discussed.

Importance and exposure in road network vulnerability analysis

The reliability and vulnerability of critical infrastructures have attracted a lot of attention recently. In order to assess these issues quantitatively, operational measures are needed. Such measures can also be used as guidance to road administrations in their prioritisation of maintenance and repair of roads, as well as for avoiding causing unnecessary disturbances in the planning of roadwork. The concepts of link importance and site exposure are introduced. In this paper, several link importance indices and site exposure indices are derived, based on the increase in generalised travel cost when links are closed. These measures are divided into two groups: one reflecting an “equal opportunities perspective”, and the other a “social efficiency perspective”. The measures are calculated for the road network of northern Sweden. Results are collected in a GIS for visualisation, and are presented per link and municipality. In view of the recent great interest in complex networks, some topological measures of the road network are also presented.

The Effect of Population Density on Infrastructure: The Case of Road Building

A cross-sectional analysis of 113 countries in 1968 indicates that population density has a significant and strong effect on total road density. An elasticity of 0.73 of road density with respect to population density was obtained. Time-series analysis confirmed this finding. An elasticity higher than unity was obtained for paved road construction. The effect on unpaved roads was somewhat smaller (0.6 elasticity) but still significant. These results suggest that population increases produce more available infrastructure/worker. The effects of both population density and per capita income on road construction are influenced by the stage of economic development. When the sample was divided into 3 income subsamples increased population density and per capita income were found to cause the substitution of paved for unpaved roads in the richer countries. At lower levels of income per capita income is less important than population density in influencing road construction since village volunteer labor can be substituted for money expenditures.