Probe vehicle-based traffic state estimation method with spacing information and conservation law

•Traffic state estimation method based on probe vehicle data is developed.•The probe vehicle data contain spacing information as well as position.•The method is incorporated with the conservation law to represent traffic dynamics.•The method does not use the fundamental diagram in order to eliminate exogenous factors.

This paper proposes a method of estimating a traffic state based on probe vehicle data that contain spacing and position of probe vehicles. The probe vehicles were assumed to observe spacing by utilizing an advanced driver assistance system, that has been implemented in practice and is expected to spread in the near future. The proposed method relies on the conservation law of the traffic flow but is independent of a fundamental diagram. The conservation law is utilized for reasonable aggregation of the spacing data to acquire the traffic state, i.e., a flow, density and speed. Its independence from a fundamental diagram means that the proposed method does not require predetermined nor exogenous assumptions with regard to the traffic flow model parameters. The proposed method was validated through a simulation experiment under ideal conditions and a field experiment conducted under actual traffic conditions; and empirical characteristics of the proposed method were investigated.