Symbols for Cockpit Displays of Traffic Information

A Web-based study assessed pilots' ability to learn and remember traffic symbols that may be shown on Cockpit Displays of Traffic Information (CDTI). These displays convey data obtained from Automatic Dependent Surveillance-Broadcast (ADS-B) and related Aircraft Surveillance Applications System (ASAS) technologies, as well as other surveillance data sources. We evaluated three aspects of using the traffic symbols when presented in isolation on a static display: intuitiveness, ease of learning, and ease of remembering the symbols. Four symbol sets were tested, each with approximately 22 symbols. Each participant saw only one of the four symbol sets. The sets used different visual features of the traffic symbol to represent the directionality, data quality, air/ground status, alert level, selection status, and pairing status of nearby aircraft. A total of 623 pilots with a broad range of experience participated in the main portion of the study. Results showed that while some conventions are well understood, such as the use of red and yellow for warnings and cautions (respectively), other conventions may be confusing and should be avoided. Two examples of confusing conventions are (a) using more than one visual feature (e.g., two different shapes) to represent the same traffic information, and (b) using similar visual features (e.g., two different outlines) to represent different traffic information. Results of the study were considered by a Federal Advisory Committee that develops standards for these traffic displays (RTCA Special Committee (SC) 186).