  Accurate modeling of lower-level controller plays an important role in the
traffic flow of automated vehicles (AVs). However, there lacks enough attention
with this respect. To address this issue, we conduct a field experiment with
two vehicles that are equipped with developable autonomous driving system,
where one can customize the upper-level control algorithm. Based on the field
experimental data, a new lower-level control model is developed and compared
with two widely used ones. The comparison results show that the proposed model
outperforms the two previous models in capturing the observed actual
acceleration, especially the troughs of the acceleration time series.
Furthermore, theoretical analysis indicates that comparing with the proposed
model, the two previous models significantly overestimate the stability region
of the traffic flow of the AVs and the capacity of stable traffic flow. Our
study is expected to further shed light on the importance of accurate
lower-level control modeling.
