4.1.1 Traffic volume/density and traffic complexity

The traffic volume/density as well as the traffic complexity — e.g. the characteristics and mix of aircraft (IFR/VFR, aircraft types, performance and equipage, etc.) and vehicle operations — are factors for consideration when implementing remote aerodrome ATS (as is the case when building/upgrading a conventional tower). The traffic volume/density and traffic complexity will drive the requirements for the visual presentation and the need for enhanced binocular functionality, as well as for other technical enablers. For each implementation, the safety assessment should consider the traffic volume/density as well as the traffic complexity related to the aerodrome when establishing the necessary functionalities of the system. Validation results from the SESAR JU programme ([20], [21], [26], [36] & [38]) indicate that, in the context of low-density aerodromes, the basic features (as described by SESAR, see Appendix 4) are considered to be sufficient. For aerodromes where traffic volume/density exceeds the low-density characteristics (as described by SESAR), validation results indicate that the need for advanced features (as described by SESAR, see Appendix 4) may be increased. However, at the same time it is acknowledged that the quality of the visual presentation is crucial; with a high-quality visual presentation, the basic features (as described by SESAR, see Appendix 4) may still be sufficient. Depending on the visual performance quality of the visual presentation, the basic features (as described by SESAR, see Appendix 4) may be sufficient for aerodromes where traffic exceeds the low-density or low-complexity characteristics. However, it is recommended that ATS providers consider using the advanced features (as described by SESAR, see Appendix 4), especially for medium-density aerodromes (as described by SESAR) and beyond. However, when implementing such features, caution should be taken with regard to the potential dependency on information intended to maintain or reach a certain level of situational awareness or capacity. Appropriate fall-back and degraded mode procedures should be developed to handle system degradations.