  In this paper, we derive second order hydrodynamic traffic models from
kinetic-controlled equations for driver-assist vehicles. At the vehicle level
we take into account two main control strategies synthesising the action of
adaptive cruise controls and cooperative adaptive cruise controls. The
resulting macroscopic dynamics fulfil the anisotropy condition introduced in
the celebrated Aw-Rascle-Zhang model. Unlike other models based on heuristic
arguments, our approach unveils the main physical aspects behind frequently
used hydrodynamic traffic models and justifies the structure of the resulting
macroscopic equations incorporating driver-assist vehicles. Numerical insights
show that the presence of driver-assist vehicles produces an aggregate
homogenisation of the mean flow speed, which may also be steered towards a
suitable desired speed in such a way that optimal flows and traffic
stabilisation are reached.
