01081146

Component

Artificial outdoor lighting plays several important roles. In addition to functional roles such as improving visibility and providing orientation, outdoor lighting is increasingly required to contribute to the lifestyle and feeling of emotional well-being of people outside at night. In this regard, outdoor lighting can help to increase the feeling of safety and security among pedestrians, as well as to enhance the attractiveness, ambience and appearance of an illuminated area. Environmentally, it is desirable to use efficient light sources with good optical control so that the targeted area is efficiently illuminated while sky glow and unwanted stray light are minimized. At present, high-pressure sodium (HPS) lamps are widely used in outdoor applications due to their high efficacy and long, reliable lifetime. The use of these lamps however, comes at the expense of good color rendering and accurate color appearance of outdoor spaces. Recently developed ceramic metal halide lamps can solve this dilemma by providing many of the advantages of HPS along with additional key features such as more natural white light and significantly better color rendering. Related benefits of these lamps for the residents and pedestrians in the areas illuminated by them might include greater ease of facial recognition and color identification. Color provides important visual information. Color differentiation and identification can contribute to one’s ability to recognize faces or identify one’s car, for example. Moreover, in the case of reporting a criminal act, accurate color naming can provide key information about the color of the suspected person’s clothing or automobile. Indeed, an earlier laboratory study conducted by Raynham et al concluded that twice the illuminance level of HPS is required to achieve the same facial recognition distance as with white light compact fluorescent sources at typical nighttime outdoor lighting levels. The advantages of high quality white light for facial recognition is already taken advantage of in the British standard for road lighting, BS5489:2003, which allows a lower lighting level to be used in residential areas if the color rendering index of the source used is over 60. Previous investigations have suggested that people want to be able to recognize strangers from a distance of 4 m in order to feel comfortable. However it is extremely likely that this “comfort zone” distance varies significantly from one person to another and also depending on the familiarity of the environment. Improving the distance for and ease of facial recognition might contribute to increasing the feeling of safety and security of pedestrians and especially for those who feel most vulnerable. Furthermore, there are numerous papers that discuss other benefits of white light, including improved peripheral visibility at mesopic lighting levels as a result of the higher scotopic/photopic ratio compared to HPS. Peripheral (off-axis) vision is important, for example, to enable pedestrians to detect a stranger approaching from the side, before the stranger can be seen or recognized in the direct (on-axis) field of view. Off-axis vision also enables drivers who are looking straight ahead to detect persons or objects before they unexpectedly move onto the driving lane. Previous laboratory studies, supported by theoretical models, have indicated that the reaction times for detection of off-axis targets are shorter under illumination by sources with higher short wavelength emission (i.e. white vs yellow) at mesopic light levels (0.001 - ~0.3cd/m2). In this paper, the authors present results from two independent field studies of the effect of lamp spectrum on visual performance at low lighting levels found outdoors at night. These studies were performed under more realistic conditions than the previous laboratory investigations referenced above. The first study focuses on benefits for pedestrians such as facial recognition and identification of colors in their residential neighborhood. The second study addresses the detection of targets in the peripheral field of view in an actual driving test outdoor at night.

01081138

English

9p

2007-4

18th Biennial TRB Visibility Symposium

CD-ROM

Figures (4) ; Tables (4)

Accuracy; Ceramic materials; Color; Crimes; Detection and identification; Drivers; Environmental impacts; Field studies; Lighting; Night; Night visibility; Pedestrians; Perception; Peripheral vision; Safety and security

Face recognition

Appearance; Artificial light; Attractiveness; Efficiency; High pressure sodium lighting; Lifetime; Metal halide lamps; Orientation; Outdoor; Users; Well being; White light

Design; Environment; Highways; Pedestrians and Bicyclists; Planning and Forecasting; Safety and Human Factors; Security and Emergencies; I21: Planning of Transport Infrastructure

TRIS, TRB, ATRI

Nov 23 2007 12:11PM

• A Review of Disability and Discomfort Glare Research and Future Direction
• Analysis of Modeled Versus On-the-Road Field Luminance of Retroreflective Signs
• Challenges to Implementation of Work Zone Lighting Guidelines
• Comparing Data Collection Scenarios Used for Examining Drivers' Sign Viewing Behavior: Closed Course Versus Open Road Environments
• Development of the Human Factors Guidelines (HFG) for Road Systems
• Driver Understanding of the Purpose of Red Retroreflective Raised Pavement Markings
• Driver-Focused Design of Retroreflective Sheeting for Traffic Signs
• Evaluation of Road-Sign Geometry Parameter Space
• Fluorescent Orange Retroreflective Raised Pavement Marker Color Recognition Study
• I-95 Corridor Mile Marker and Ramp Designation Signing
• Modern Pavement Marking Systems: The Relationship Between Optics and Nighttime Visibility
• Pavement Marking Visibility: Brighter Versus Wider
• Performance Assessment of Vehicle Headlamps
• Recommendations for Minimum Pavement Marking Retroreflectivity Values Based on Tarvip Analyses
• Revealing Power and Road Lighting Design
• The Relationship of Vertical Illuminance to Pedestrian Visibility in Crosswalk