The Evolutionary Air-ground Co-operative ATM Concepts (EACAC) study of the Freer-Flight project investigates the delegation by the controller to the pilot, of some tasks related to separation assurance. Starting from the analogy of visual clearances, EACAC investigates the possibility of giving electronic clearances. One of the issues of the study deals with the appropriate assistance scheme to be provided to the pilot, considering the proposed concept of limited delegation. The “scales of separations” is one of the levels of assistance envisaged. Two models of turns and their appropriateness for lateral scales of effects are investigated. The scales of separations implementing these models will be evaluated by pilots, first through a cockpit environment in a stand-alone mode (end 1999), and then using a cockpit simulator in a real-time simulation with controllers (mid 2000).