Sustainability assessment of road networks: A new perspective based on service ability and landscape connectivity

With expanding infrastructure, roads which as a main method of transport in inland areas have been increasing rapidly in developing countries. Their interconnectedness determines a city's sustainability. To avoid using excessive indicators, this paper takes the Wu'an city as a study area to propose a system to assess the development of the road network that focuses on two indicators: one is the service ability which indicates the value of roads, and the other is landscape connectivity which is used to measure the roads influence on the environment. The results reveal that the density or length of roads is not the exclusive indicator used to determine service ability, while reasonable and effective road networks are also crucial elements. So the construction of roads should be explicit about the service objective. And the landscape connectivity used in this study not only reflects the effects of roads on ecological land but also recognizes important patches (whose landscape connectivity is high). According to the visible landscape connectivity changes, it's demonstrated that road is interrelated with landscape connectivity. Where the road is, there will be worse landscape fragmentation and connectivity, especially in the neighboring areas. As the results show that the obvious impacts variations of landscape connectivity are almost focused on the habitat adjacent to the roads. The study also demonstrates how the results of such an analysis vary with species traits (dispersal capabilities) and shows that the probability of connectivity which contributes to the overall landscape connectivity increases with larger dispersal distances. It is suggested that a reasonable scale should be considered when measuring these influences. Our study provides a useful diagnosis and helpful information for assessing the road networks. This analysis can be further applied to judge whether road construction is worthy enough so as to promote the sustainable development of road transportation by creating a balance between the service ability and the influence on the ecological system.