Obstacle detection: A pilot study investigating the effects of lamp type, illuminance and age

A novel apparatus was used to examine the effect of light source, illuminance and observer’s age on the ability to detect obstacles in peripheral vision, simulating a raised paving slab under mesopic visual conditions. The data collected were used to determine the height of obstacles above the paving surface required for 50% detection. From these detection heights it was determined that: (1) obstacle detection was influenced by illuminance, the 50% detection height being lower at 20 lux than at 0.2 lux, (2) the young observers (<45 years old) showed the smaller 50% detection height at 0.2 lux, but at 20 lux there was no difference in obstacle detection height between the younger and older (>60 years old) age groups, and (3) obstacle detection was affected by lamp type at 0.2 lux, with the 50% detection height decreasing as lamp S/P ratio increased, but at 2.0 and 20 lux there was no significant difference between the three test lamps.