A lantern color vision test for the rail industry

Abstract

BACKGROUND: Correct identification of wayside signal colors is critical for safe operation of railway equipment. However, evaluating color discrimination using just a screening test may not be occupationally relevant. METHODS: A lantern test (CNLAN) was designed to provide a functional assessment of color discrimination for the rail industry. It was validated against a simulated field trial. 81 individuals with normal color vision and 74 individuals with congenital red-green defects participated. Color vision was classified using the Nagel Anomaloscope. RESULTS: Using a criterion based on the worst-normal performance, 97% of the individuals with a color vision defect failed both the CNLAN and simulation trial. This value is slightly lower than the 100% who failed both the Ishihara test and simulation. However, the Ishihara test also failed 3.7% of the color-normals who passed both the simulation and lantern, whereas by definition none of the color-normals failed the lantern. CONCLUSIONS: This lantern test provides a reasonable functional assessment of one's ability to identify rail signal colors; especially when a strict failing criterion is applied to screening tests.