Evolution of the second-story city: the Minneapolis Skyway System
This research describes the growth of the Minneapolis Skyway network and aims to determine if the growth of the system has followed a predictable path. We hypothesize that the system expanded to the places in which it was valued the most. The point accessibility of each block lying within and adjacent to the connected system for each expansion year is calculated and used to predict the expansion of the Skyway System. In order to determine how often the expansion connected the blocks with higher accessibility, a connection-choice logit model relating the probability of joining the network (in a given year) to accessibility measures and network size was employed. The results disclose that accessibility is a significant explanatory factor of network growth. In accordance with the findings from the logit model, a network-growth simulation model was then developed on the basis of the strongest-link assumption (ie for a link to be constructed, it must be ranked the highest in terms of increasing accessibility between the two blocks it connects). The results show that the simulation model performs well in predicting the sequence of skyway additions on the basis of the myopic strongest-link assumption. This suggests that—although various physical, economic, regulatory, and legal factors may have played a role—accessibility remains an important factor in predicting which links are connected during the growth of the Minneapolis Skyway network.