A hybrid fundamental diagram for modeling mixed human and automated traffic flow

Automated and partially automated vehicles will substantially change the way traffic flows, even at low market penetration rates. While the primary tool for analysis of mixed human-piloted and automated traffic has been microscopic simulation, the use of macroscopic traffic simulation allows for larger-scale simulations. With that in mind we propose a simple numerical method to estimate the composite fundamental diagram of mixed human-piloted and automated traffic flow from the fundamental diagrams of 100% human-piloted and 100% automated traffic flow and conduct calibrated microscopic traffic simulations to produce fundamental diagrams for how mixed traffic flow may behave at different market penetration rates. This method is demonstrated for both an automated vehicle and a commercially available adaptive cruise control vehicle. The proposed method is shown to be able to accurately estimate the shape of the fundamental diagram for arbitrary automated vehicle market penetration rates and the results provide insight into how the mixed traffic flow may behave at the macroscopic level.