  We design and experimentally evaluate a hybrid safe-by-construction collision
avoidance controller for autonomous vehicles. The controller combines into a
single architecture the respective advantages of an adaptive controller and a
discrete safe controller. The adaptive controller relies on model predictive
control to achieve optimal efficiency in nominal conditions. The safe
controller avoids collision by applying two different policies, for nominal and
out-of-nominal conditions, respectively. We present design principles for both
the adaptive and the safe controller and show how each one can contribute in
the hybrid architecture to improve performance, road occupancy and passenger
comfort while preserving safety. The experimental results confirm the
feasibility of the approach and the practical relevance of hybrid controllers
for safe and efficient driving.
