Fig. 7.

Path dependence in street-network sprawl. SNDi of recent (2000 to 2013) construction is closely correlated with that of the earlier road stock in 1975 (countries, A) and 1990 (cities, B). Circle size denotes the length of original road stock, while color indicates the scale of recent construction. Only cities and countries with at least 100 km of new roads are shown. Linear fits characterizing the persistence relationship (gray shaded confidence region) are nearly parallel to the $45^{○}$ line of perfect persistence (dark gray line), indicating a relatively uniform shift (on average $\mathrm{\Delta }$SNDi$=+$1.56 for cities, $+$1.26 for countries) (Table 3) away from earlier high connectivity. A zoomable version of this figure with labels for cities and countries is in SI Appendix.