  We study a hierarchy of models based on kinetic equations for the
descriptions of traffic flow in presence of autonomous and human--driven
vehicles. The autonomous cars considered in this paper are thought of as
vehicles endowed with some degree of autonomous driving which decreases the
stochasticity of the drivers' behavior. Compared to the existing literature, we
do not model autonomous cars as externally controlled vehicles. We investigate
whether this feature is enough to provide a stabilization of traffic
instabilities such as stop and go waves. We propose two indicators to quantify
traffic instability and we find, with analytical and numerical tools, that
traffic instabilities are damped as the penetration rate of the autonomous
vehicles increases.
