Modeling heterogeneous traffic with cooperative adaptive cruise control vehicles: A first-order macroscopic perspective

This paper proposes a modeling framework to characterize steady-state traffic flow relations for heterogeneous traffic composed of both standard (S) and Cooperative Adaptive Cruise Control (CACC, labeled C here) vehicles, capturing the impact of C market penetration and vehicle sequence within a lane. The resulting parameterized fundamental diagram is then integrated with a first-order macroscopic traffic model, allowing us to characterize the operational performance on a network for heterogeneous traffic with varying C market penetration rates. This approach is demonstrated through an illustrative case study which considers a small freeway section with time-varying demand, merging traffic from an entrance ramp, and C market penetration ranging from 0.0–1.0. The results indicate that maximum throughput does not change appreciably as C traffic is first introduced, but eventually increases significantly for mid-to-high C penetration rates. Additionally, it shows that increasing C market penetration and separating vehicle classes slows upstream congestion propagation.