Highway Traffic State Estimation with Mixed Connected and Conventional Vehicles

TL;DR

This paper presents a macroscopic model-based method for estimating overall traffic density and flow in mixed traffic conditions using connected vehicle data and a Kalman filter, requiring minimal sensor measurements.

Contribution

It introduces a new linear time-varying model for the percentage of connected vehicles and an estimation algorithm validated through simulations.

Findings

Accurate traffic state estimation with minimal sensors

Effective estimation of connected vehicle percentage

Validated approach using second-order traffic model

Abstract

A macroscopic model-based approach for estimation of the traffic state, specifically of the (total) density and flow of vehicles, is developed for the case of "mixed" traffic, i.e., traffic comprising both ordinary and connected vehicles. The development relies on the following realistic assumptions: (i) The density and flow of connected vehicles are known at the (local or central) traffic monitoring and control unit on the basis of their regularly reported positions, and (ii) the average speed of conventional vehicles is roughly equal to the average speed of connected vehicles. Thus, complete traffic state estimation (for arbitrarily selected segments in the network) may be achieved by merely estimating the percentage of connected vehicles with respect to the total number of vehicles. A model is derived, which describes the dynamics of the percentage of connected vehicles, utilizing only well-known conservation law equations that describe the dynamics of the density of connected vehicles and of the total density of all vehicles. Based on this model, which is a linear time-varying system, an estimation algorithm for the percentage of connected vehicles is developed employing a Kalman filter. The estimation methodology is validated through simulations using a second-order macroscopic traffic flow model as ground truth for the traffic state. The approach calls for a minimum of spot sensor-based total flow measurements {according to a variety of possible location configurations.