Over the past 300 years, scientific observations have revealed the significant influence of circadian rhythms on various human functions, including sleep, digestion, and immune system regulation. Access to natural daylight is crucial for maintaining these rhythms, but modern lifestyles often limit its availability. Despite its importance, there is a lack of a comprehensive design framework to assist designers. This study proposes an architectural design framework based on the review of literature, lighting-related codes and standards, and available design and analysis tools that guides the creation of lighting systems supporting healthy circadian rhythms. The framework outlines key decision-making stages, incorporates relevant knowledge, and promotes the integration of dynamic lighting techniques into building design. The proposed framework was presented to a group of design professionals as a focus group and their feedback on the relevance and usability of the tool was obtained through a survey (n = 10). By empowering designers with practical tools and processes, this research bridges the gap between scientific understanding and design implementation, ensuring informed decisions that positively impact human health. This research contributes to the ongoing pursuit of creating lighting environments that support healthy circadian rhythms and promote human well-being.

In the last decade, pedestrian fatalities at night, especially at midblock locations, have been increasing at an alarming rate. Lighting is an effective countermeasure in reducing nighttime crashes. However, few studies have evaluated the effects of crosswalk lighting on pedestrian visibility at midblock locations. There is an existing need to develop lighting designs that increase pedestrian visibility. Further, the safety effects of lighting have never been directly compared to other pedestrian-crossing treatments (such as flashing signs, rectangular rapid flashing beacons (RRFBs), etc.). Thus, in order to make effective recommendations for increasing nighttime pedestrian visibility, it is important to compare the visibility benefits of crosswalk lighting designs with and without pedestrian-crossing treatments. This study evaluated the visual performance of five midblock crosswalk lighting designs along with two pedestrian safety countermeasures at three light levels on a realistic midblock crosswalk. Visual performance was measured by calculating the distance at which the participants could detect a child-sized mannequin under the evaluated conditions. The results showed that midblock crosswalks should be illuminated to an average vertical illuminance of 10 lux to ensure optimal pedestrian visibility. Lighting designs that render the pedestrian in positive contrast (area in front of the crosswalk is illuminated) are recommended to increase pedestrian visibility. It is also recommended that pedestrian-crossing treatments, such as RRFBs and flashing signs, should be used with lighting to increase nighttime visibility.

Light levels recommended for parking facilities should be backed by empirical research that accounts for all users. In the current study, pedestrians’ and drivers’ visual performance and their perceptions of safety, comfort, and visibility were evaluated at a parking garage and at parking lots with asphalt and concrete pavements under three light source types (high-pressure sodium luminaire, 3000 K light emitting diode [LED] luminaire, and 5000 K LED luminaire) and at multiple light levels. Visual performance involved facial and hand recognition, wheel stop detection, detection of a side-facing pedestrian, and detection of a vehicle backing up from a parking spot. Perceptions of safety, comfort, and visibility were assessed by means of a questionnaire. Results showed that in the parking garage, an increase in light level beyond 10 lux of average horizontal pavement illuminance did not result in a statistically significant increase in visual performance or perceptions of safety, comfort, and visibility. For parking lots of asphalt and concrete pavements, this plateauing was observed at the 2 lux light level. No statistical differences were observed between the light source types for the visual performance tasks, but the perceptions of safety, comfort, and visibility were highest for the 5000 K LED luminaires.

This paper describes the visibility experiment conducted as part of a research effort to establish the durability of pavement markings in an on-road installation. Six marking technologies were installed on a portion of Route 460 in Blacksburg, Virginia. A human factors experiment in natural rain conditions was performed to establish the visibility needs of the driver. The retroreflectivity of the markings was measured at intervals of 2 to 5 months, with six measurements over the course of 23 months (these data are discussed in a separate paper). Previous research suggested that a minimum retroreflectivity of 150 mcd/m²/lx should be maintained to meet drivers' visibility needs. As part of this research, a human factors experiment was conducted to test the validity of this recommendation. The distance at which participants could detect the end of a pavement marking was measured as well as the retroreflectivity of the marking at those points. The relationship of detection distance and retroreflectivity found in this study suggests that as retroreflectivity increases beyond 150 mcd/m²/lx, there are diminishing returns on detection distance. This finding suggests that the recommended minimum is appropriate for providing increased visibility for drivers, while keeping retroreflectivity requirements at a reasonable level for marking manufacturers.

Introduction: In 2009, the World Health Organization identified vehicle crashes, both injury-related and fatal, as a public health hazard. Roadway lighting has long been used to reduce crashes and improve the safety of all road users. Ocular light exposure at night can suppress melatonin levels in humans. At sufficient light levels, all visible light wavelengths can elicit this response, but melatonin suppression is maximally sensitive to visible short wavelength light. With the conversion of roadway lighting to solid state sources that have a greater short wavelength spectrum than traditional sources, there is a potential negative health impact through suppressed melatonin levels to roadway users and those living close to the roadway. This paper presents data on the impact of outdoor roadway lighting on salivary melatonin in three cohorts of participants: drivers, pedestrians, and those experiencing light trespass in their homes. Methods: In an outdoor naturalistic roadway environment, healthy participants (N = 29) each being assigned to a cohort of either pedestrian, driver, or light trespass experiment, were exposed to five different solid state light sources with differing spectral emissions and one no lighting condition. Salivary melatonin measurements were made under an average roadway luminance of 1.0 cd/m² (IES RP-18 Roadway Lighting Requirements for expressway roads) with a corneal melanopic Equivalent Daylight Illuminances (EDI) ranging from 0.22 to 0.86 lux. Results: The results indicate that compared to the no roadway lighting condition, the roadway light source spectral content did not significantly impact salivary melatonin levels in the participants in any of the cohorts. Conclusions: These data show that recommended levels of street lighting for expressway roads do not elicit an acute suppression of salivary melatonin and suggest that the health benefit of roadway lighting for traffic safety is not compromised by an acute effect on salivary melatonin.