Light Levels for Parking Facilities Based on Empirical Evaluation of Visual Performance and User Perceptions

Impacts of average illuminance, spectral distribution, and uniformity on brightness and safety perceptions under parking lot lighting

“…In another field study, 8 ratings of safety for asphalt-paved parking lots began to plateau between 2 and 10 lx, which is lower than the illuminances at which safety ratings began to plateau in the present studies. The range of average illuminances used in that study differed from those in the present study (1 to 12.5 lx), and illumination was always relatively uniform with a maximum:minimum ratio of 5:1.…”

“…These findings were extended in a series of laboratory and analytical studies that identified a spectral sensitivity model that predicted the relative scene brightness of a lighting installation. 9,10 Consistent with these findings, Bhagavathula and Gibbons 8 reported improved perceptions of safety, comfort and visibility in a parking lot illuminated by a 5000 K light-emitting diode (LED) source compared to a 3000 K LED source or to HPS illumination. Based on the modeling from Rea et al .…”

“…26 Importantly, the laboratory experiments in this study yielded results that were largely consistent with those from published field research. 1,8,13,18 They indicate that models of spectral sensitivity for scene brightness 9,10 in conjunction with analytical predictions of safety incorporating both uniformity and spectrally adjusted brightness quantities can be used to make reasonable predictions of perceived safety in parking lot lighting. Further efforts to test these predictions in a priori tests and not only in post hoc comparisons to published literature are underway.…”

“…1 were primarily high pressure sodium (HPS) and metal halide (MH) lamps. Bhagavathula and Gibbons 8 reported that as the average illuminance in a parking lot increased from 2 lx to 10 lx, perceptions of safety, comfort and visibility did not improve substantially.…”

Integrating Research on Safety Perceptions Under Parking Lot Illumination

“…Rather, as the average parking lot illuminance increased, the ratings began to exhibit a plateau. Similar findings have been noted subsequently by Bhagavathula and Gibbons (2019). Interestingly, Boyce et al (2000) found that ratings for urban parking lots were slightly, but consistently, lower ( Figure 3) than for suburban parking lots lighted to the same average illuminance.…”