Laboratory Results
Major Findings
Greater illuminance uniformity promoted greater perceptions of safety across all tested average illuminance levels (Figure 4A)
Greater uniformity (2:1) promoted greater perceptions of safety using less energy (Figure 4A).
Modest gains in perceived safety could also be realized by increasing the lighting's spectral distribution from 2850 K to 5800 K (Figure 4B).
Figure 4. Safety ratings recorded for different illuminance uniformity (A) and spectral distribution (B) conditions for the four simulated parking lot lighting conditions depicted in Figure 2. The curves’ upward slope confirms that safety perception improves with higher average illuminance levels, but panel A shows there may be a limit to safety perceptions of low-uniformity lighting designs, even at relatively high (~20 lx) average illuminance levels, as indicated by the roughly equivalent safety ratings for 5 lx with the 2:1 illuminance uniformity ratio vs. 20 lx with the 15:1 illuminance uniformity ratio (highlighted with green dashed lines).