Classically, fundamental diagrams are estimated from aggregated data at a specific location. Such a measurement method may lead to inconsistency which mainly explain the controversy about their shape. This paper proposes a new estimation method based on passing rate measurements along moving observer paths. Under specific assumptions, it can be proved that in congestion passing rate is constant whatever the traffic flow states are. This property allows (i) to prove that a linear fundamental diagram is suitable to represent traffic flow behavior involved in the NGSIM dataset; (ii) to fit its two parameters: the congested wave speed and the jam density. Finally, simulations of vehicle trajectories are carried out with the Newell's simplified car-following model to test the estimated fundamental diagram. It is found that the estimated parameters provide accurate vehicle trajectories.
Abstract