Assessing route redundancy of freeway networks in Mega-city regions

Abstract

• Assess the route redundancy of freeway networks in mega-city regions. • Propose diversity and dispersion of alternative paths as two complementary measures. • Assess route redundancy of mega-city freeway networks at network and city levels. • Consider three major mega-city regions of China in the case studies. In this paper, we investigate the performance of freeway networks in mega-city regions from the perspective of route redundancy—the provision of alternative routes for travelers when their primary routes are disrupted by disasters. Specifically, route redundancy is assessed with two complementary dimensions: the diversity and dispersion of alternative routes. The former represents the number of alternative routes without disruptions, and the latter reflects the robustness of this number during disruptions. Three typical mega-city regions in China, namely the Beijing-Tianjin-Hebei, the Guangdong-Hong Kong-Macao Greater Bay Area, and the Yangtze River Delta—are examined as case studies. Results indicate that travelers in first-tier cities (i.e., national economic or political centers) may have inadequate route redundancy. Route diversity increases when more topological cycles are traversed by numerous alternative routes. Additionally, alternative routes of the peripheral cities in mega-city regions are less dispersed, which cause their lack of redundancy and should be improved.