An Analytical Approach for Estimating the Highway Capacity Manual Signalized Intersection Delay Variability

This article developed a generalized model incorporating three stochastic input variables in the Highway Capacity Manual (HCM) delay equation and analyzed the delay variability explicitly considering variations in key input variables including traffic volume, effective green time, and saturation flow rate. An integration method was used for calculations of mean and variance of the HCM delay. Unlike the previous Expectation Function Method, the proposed integration method can be applied for both undersaturated and oversaturated situations. The applicability of the proposed methodology was demonstrated through a hypothetical case study for a lane group at an isolated signalized intersection. The effects of stochastic variables (e.g., traffic volume, saturation flow rate, and effective green time) and correlations among these variables in the HCM delay were examined.