Can road lighting design guidance for ensuring facial recognition be justified

The recommendations for P class road lighting in CIE 115:2010 include additional requirements ‘ if facial recognition is necessary ’. Those requirements are minimum levels of vertical or semi-cylindrical illuminance. A review of road lighting research and guidance found no robust basis for the recommended levels, nor any evidence that semi-cylindrical illuminance offers an advantage over other metrics. It is suggested that facial identity recognition, a procedure used in previous lighting research, is not a suitable task and instead that facial emotion recognition is used, i.e. the ability to distinguish between facial expressions. Research using facial emotion recognition does not support the proposal in CIE 115:2010 that higher colour rendering enhances facial recognition. While such research also suggests optimal light levels, the literature is yet insufficient to make robust recommendations because it does not consider a sufficient range of observer ages, observed-person skin tones, nor the impact of high light levels on the observed person, and there is insufficient replication. It is therefore suggested that the additional requirements for facial recognition be omitted from the upcoming revision of CIE 115:2010.