Are traffic signs safe?
The “keep left” sign caught the sun behind me and acted like a mirror.
I was blinded.
White Paper
Initial assessment of Solar-Induced Glare Risk from Microprismatic Retroreflective Traffic Signs in Central Island Installations
Date
2026-03-20
Executive Summary
This paper raises a road safety concern regarding the use of microprismatic retroreflective traffic signs installed on central traffic islands on near east–west aligned roads. An observed event in Robina, Queensland demonstrated a sustained glare condition lasting minutes, consistent with disabling glare (veiling luminance) producing a near white-out effect for an approaching driver. The condition arises from a predictable interaction between known high-efficiency retroreflective material, central island head-on sign geometry, constrained vehicle alignment toward the centreline, and morning solar position. This is not a transient flash. It is a repeatable alignment condition capable of impairing driver visibility over distance. Current standards validate material performance and sign usage, but there is no clear evidence that solar-induced glare under these combined conditions has been explicitly assessed. Accordingly, it is reasonable to question whether such installations have been adequately evaluated for this specific risk, given the potential for a serious traffic hazard arising from a road safety device.
Purpose
To raise a road safety concern regarding the use of microprismatic retroreflective materials in traffic signs installed on central islands on near east–west aligned roads, where observed conditions indicate potential for sustained disability glare affecting drivers.Background
Microprismatic retroreflective materials are widely used in traffic signage due to their high efficiency in returning light toward a source, primarily for night-time visibility under vehicle headlights. This reflective behaviour is well understood. Short-duration glare or “flash” is a known occurrence under normal use.
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