The current European Air Traffic Management (ATM) system will be unable to cope with the projected increase in air traffic, and there is a need to ensure that its evolution through new technologies, structures, procedures and functions, in order to increase capacity, is not to the detriment of safety. Current methodologies consider safety, efficiency and capacity as separate parameters and do not attempt to express the relationship between them. There is therefore a requirement to address methodologies and develop indicators for safety, efficiency and capacity assessment across the spectrum of operational and functional needs of ATM.