  This article studies the problems of distributed dynamic platoons control and
smart junction crossing optimization for a mixed traffic flow with connected
automated vehicles(CAVs) and social human-driven vehicles(HDVs) in a smart
city. The goal of this two-part article is to provide an automatic decision
framework to ensure the safe and efficient cruising and crossing junctions with
multiple dynamic and resilient platoons CAVs, while against the social driving
behaviors(SDBs) of the HDVs considered as surrounding vehicles(SVs) and unknown
traffic lights connected by Cellular-Vehicle-to-X (C-V2X) infrastructure. We
shall show that despite the nonlinearity, non-smoothness, and uncertainty of
mixed traffic flows in smart cities, the solutions of safe, efficient, and fuel
economic platoon CAVs control for the above problems can be solved by our
proposed automatic decision and smart crossing assistant system(ADSCAS) that
includes four decision stages and six cruising states characterized within this
article. More precisely, in part I, we provide a dynamic platoon management
strategy to determine the platoon size with respect to the SDBs of the
preceding HDVs and upcoming traffic lights, where the dynamic platoon size is
composed of minimizing safe distances and nonlinear functions of the platoon's
cruising velocity. We also present the decision and switching scheme for a
finite state machine of platoons in the ADSCAS, the design of the reference
trajectory planning, and the solution of the fuel economic optimization
problem.
