  Before reaching full autonomy, vehicles will gradually be equipped with more
and more advanced driver assistance systems (ADAS), effectively rendering them
semi-autonomous. However, current ADAS technologies seem unable to handle
complex traffic situations, notably when dealing with vehicles arriving from
the sides, either at intersections or when merging on highways. The high rate
of accidents in these settings prove that they constitute difficult driving
situations. Moreover, intersections and merging lanes are often the source of
important traffic congestion and, sometimes, deadlocks. In this article, we
propose a cooperative framework to safely coordinate semi-autonomous vehicles
in such settings, removing the risk of collision or deadlocks while remaining
compatible with human driving. More specifically, we present a supervised
coordination scheme that overrides control inputs from human drivers when they
would result in an unsafe or blocked situation. To avoid unnecessary
intervention and remain compatible with human driving, overriding only occurs
when collisions or deadlocks are imminent. In this case, safe overriding
controls are chosen while ensuring they deviate minimally from those originally
requested by the drivers. Simulation results based on a realistic physics
simulator show that our approach is scalable to real-world scenarios, and
computations can be performed in real-time on a standard computer for up to a
dozen simultaneous vehicles.
