Comparability of Urban Street Networks: Consideration of the Size Effect in the Evaluation of Network Characteristics and a Proposal for Determining an Appropriate Size of the Catchment Area for Pedestrian Networks

Abstract

For the analysis of urban networks indicators, like average node degree, connectivity and betweenness centrality, are widely used. Their values are calculated for a catchment area of the network. This research investigates if and to what extent the size of the catchment area influences the indicator’s values. A methodology for determining the size of catchment area is proposed and recommendations for its appropriate size for pedestrian network analysis are offered. For the mathematical deduction of the relationship between the size of the catchment area and the indicator values an idealized regular network is used as a reference model. We found that the size effect on indicator values is prominent. It decreases exponentially as the size of the catchment area increases. The size effect is notable until a side length of the catchment area that equals 50 times the average street length, while the variation is still acceptable if it is 30 to 40 times the average street length. The typical average street length in cities is about 100 meters, a catchment area larger than 4000 x 4000m2 is not necessary. This reference model can also be used to evaluate real networks and to compare them with an idealized case.