  Earlier work has established a decentralized optimal control framework for
coordinating online a continuous flow of connected automated vehicles (CAVs)
entering a control zone and crossing two adjacent intersections in an urban
area. A solution, when it exists, allows the vehicles to cross the
intersections without the use of traffic lights, without creating congestion on
the connecting road, and under the hard safety constraint of collision
avoidance. We establish the conditions under which such solutions exist and
show that they can be enforced through an appropriately designed feasibility
enforcement zone that precedes the control zone. The proposed solution and
overall control architecture are illustrated through simulation.
