Incorporating accessibility-based equity into stochastic road network design problem: sensitivity analysis and policy Implications

This paper aims at examining the sensitivity of an accessibility-based equity measure in the context of the stochastic road network design problem. An equity optimization model system based on the bi-level programming approach is proposed, where the upper level problem addresses equity optimization under road investment constraint and the lower level deals with a user equilibrium model reflecting route choice behavior with varied link capacity improvements. An accessibility-based equity measure is defined in terms of the Gini coefficient. To illustrate the applicability of the model, an empirical study using data collected in Dalian City, China is carried out. Results demonstrate that the accessibility-based equity measure can be applied to measure distributional differences in zonal accessibility. Comparative results also implicate that policy makers may need to trade-off the levels of zonal accessibility and the accessibility distribution.