On-Line Measure of Shockwaves for ITS Applications

Abstract

The formation of shockwaves demarking boundaries between different flow states in time-space domains has been well studied and documented in the literature. Previous research concentrated on theoretical and mathematical analyses of shockwaves, providing valuable insights into shockwave phenomena. In the past few years, the traffic signal systems community has witnessed an increasing interest in adaptive control algorithms. These algorithms strive to achieve real-time platoon accommodation by assuming platoon speed and dispersion characteristics in order to predict its time of arrival at the downstream signal. Instead of assuming platoon speed and dispersion characteristics, we propose an on-line analysis of shockwaves at the downstream intersection to achieve the same purpose. This paper introduces a new metric that can detect and quantify shockwaves formed as a result of a suboptimal offset at an intersection. The new metric, the F′ model, captures the effects of shockwaves using cycle-based tabulation of advance detector occupancy and count. A discriminant analysis is conducted to develop thresholds to which F′ values can be compared to estimate the offset performance. The metric introduced in this paper can be used for implementing adaptive offset tuning algorithms in a traditional closed loop coordinated traffic signal system.