Direct perception biases with maritime navigation displays of collision risk

Maritime navigation systems need to assist judgments about safe separations and avoidance manoeuvres. Collision Danger Sectors (CDS) are a proposed visualisation for radar displays intended to support the direct perception of impending traffic separation violations. We report an evaluation of the CDS display format in a laboratory study of navigation decision-making involving judgments of safe separations. Contrary to prediction, the CDS display did not bias decision making towards neglecting rules about track crossing. The CDS display did encourage excessive avoidance manoeuvres at higher angles of approach. A marked increase in response time with angle of approach was also evident, indicating a need for decision-aiding.