Improving the safety of vulnerable road users like pedestrians, roadworkers, and cyclists at night is crucial, as driver visual limitations contribute significantly to their high crash involvement in darkness. A primary approach to enhancing safety is increasing their conspicuity, meaning they are recognised as a person, not merely detected as an ambiguous object.

Research highlights the effectiveness of placing retro-reflective materials on the major moveable joints (ankles, knees, waist, shoulders, elbows, wrists). When illuminated by headlights, this configuration creates a strong sense of ‘biological motion’ or ‘biomotion’. Biological motion perception allows the visual system to recognise human movement from minimal cues, such as point-light displays attached to joints. Observers can easily identify the human form and even infer activities, gender, or emotions from such displays. Studies show that marking just the ankles and knees can enable observers to readily describe the biological motion of a walker.

Biomotion clothing significantly increases the distance at which drivers perceive a person compared to configurations like high visibility vests. One study found that drivers first responded to pedestrians wearing biomotion at 3 times longer distances than those wearing a vest (148.2 m vs 43.4 m) and over 26 times longer than those in black clothing (148.2 m vs 5.6 m). These benefits were consistent across different headlight beams and for drivers of varying ages, and also observed in cluttered environments and with glare. Beyond simple detection, biomotion helps drivers perceive a pedestrian's actions and walking direction, essential for judging potential roadway entry. Drivers recognised walking direction 2.3 times further with biomotion clothing compared to a vest. Eye movement data shows biomotion attracts driver attention sooner, and the human form is recognised faster than with a vest.

Importantly, the benefits of biomotion are evident even when the person is standing still, showing the advantage isn't solely dependent on movement but also on highlighting the human form. A study comparing a standard ANSI Class II vest, a Vest + Ankles configuration, and a Full Biomotion configuration found that adding reflective ankle straps to a vest substantially increased response distances compared to the vest alone. The response distances for the Vest + Ankles were similar to the Full Biomotion configuration, suggesting that marking the ankles provides significant conspicuity value. Pedestrian movement generally leads to greater response distances, especially when combined with reflective material on limbs. Pedestrians facing the oncoming vehicle are also perceived at greater distances than those viewed from the side.

Evidence from this research was key in changing Australian and New Zealand standards for roadworker high visibility clothing to include retro-reflective strips in the biomotion configuration.

Despite the proven effectiveness of biomotion and other strategies, a major challenge is the lack of awareness among vulnerable road users regarding the best ways to increase their night-time conspicuity. Many are unaware of the importance of retro-reflective materials. Studies indicate pedestrians often overestimate their own conspicuity to drivers at night. Drivers also exhibit dangerous misunderstandings, such as overdriving the useful range of their headlights. Educational interventions have shown potential in improving understanding of night vision limitations and promoting the use of conspicuity-enhancing clothing.