Characterizing and measuring transportation infrastructure diversity through linkages with ecological stability theory

Transportation infrastructure is critical to any community. Disturbances such as natural hazards can hinder transportation infrastructure performance impacting a community’s quality of life through disruptions in service and effects on interdependent systems. Ecological systems are robust and resilient and have similarities with infrastructure systems. Diversity is a fundamental element of ecological resilience and is recognized as an important factor in transportation resilience. However, measures of transportation diversity are not well-developed. Accordingly, this paper adapts the ecological diversity concepts of richness and evenness to develop an approach to characterize transportation system diversity and distinguishes the approach from existing methods. Measures of transportation functional richness and evenness are derived and applied to New York City at the zip code level. The results facilitate identification of zip codes in New York City with varying levels of transportation diversity. Those zip codes with low diversity generally have limited availability (low richness) and disproportionate distribution (low evenness) of alternative transportation modes. Further, these zip codes are potentially susceptible to system disturbances as a consequence of routine disruptions or natural hazards. For instance, many low diversity zip codes are in hurricane evacuation zones. Limited complementarity in the transportation system of these zip codes will likely impact evacuations during hurricanes and recovery to pre-disturbance performance levels. Ultimately, the transportation diversity approach presented should lead to better understanding of transportation system characteristics such as inherent and augmented complementarity, which will enhance transportation system performance in urban communities.