Towards Insect-Friendly Road Lighting—A Transdisciplinary Multi-Stakeholder Approach Involving Citizen Scientists

(1) The project “Tatort Streetlight” implements an insect-friendly road light design in a four year before–after, control–impact (BACI) approach involving citizen scientists. It will broaden the stakeholder interests from solely anthropogenic perspectives to include the welfare of insects and ecosystems. Motivated by the detrimental impacts of road lighting systems on insects, the project aims to find solutions to reduce the insect attraction and habitat fragmentation resulting from roadway illumination. (2) The citizen science approach invites stakeholders to take part and join forces for the development of a sustainable and environmentally friendly road lighting solution. Here, we describe the project strategy, stakeholder participation and motivation, and how the effects of the alternative road luminaire and lighting design can be evaluated. (3) The study compares the changes in (a) insect behavior, (b) night sky brightness, and (c) stakeholder participation and awareness. For this purpose, different experimental areas and stakeholders in four communities in Germany are identified. (4) The project transfers knowledge of adverse effects of improperly managed road illumination and interacts with various stakeholders to develop a new road lighting system that will consider the well-being of street users, local residents, and insects.

ASSESSMENT OF ROAD LIGHTING PERFORMANCE FOR TRAFFIC INTENSITY AND TRAFFIC DETECTION BASED LIGHTING ADAPTATION

Amongst many road lighting design criteria, energy performance plays an important role as it has a direct link to operational costs, potential reduction of carbon dioxide emissions, mitigation of obtrusive light, and its impact on the night-time environment in urban and con-urban settlements. The energy energy performance of road lighting is conveniently described by the pair of normative numerical indicators PDI and AECI established in European standards. This paper aims to present typical values of the AECI (Annual Energy Consumption Indicator) for different combinations of road arrangements, road widths, lighting classes and light source technologies to illustrate what benchmarks can be expected using this assessment system. Essential part of this paper is focusing on assessment of the performance for traffic intensity and traffic detection based lighting adaptation.

THE EFFECT OF CHANGES IN LIGHT LEVEL ON THE NUMBERS OF CYCLISTS

Cycling has a range of benefits and should be encouraged, but darkness may put people off from cycling due to reductions in visibility, road safety and personal security. We summarise analyses of observational data to confirm the negative impact darkness has on cycling rates. Using a Case / Control method that accounts for confounding factors such as time of day and seasonal variations in weather, we demonstrate a consistent effect of darkness across different locations and countries. The size of this effect varies though, suggesting certain unknown factors may be important in mediating the impact of darkness on cycling rates. One factor that is known to mediate the effect is road lighting. We show that increased illuminance can offset the reductions in cyclists caused by darkness and also that there may be an optimal illuminance after which no further benefits may be achieved.

OPTIMISING ROAD LIGHTING TO REDUCE ROAD TRAFFIC CRASHES

Pedestrians and motorcyclists are vulnerable road users, being over represented in road traffic collisions (RTCs). One assumed benefit of road lighting is a reduction in RTCs after dark by countering the impairment to the visual detection of hazards that occur after dark. One way to optimise the use of road lighting is to light only those sections of road where light level, and hence visibility, is an important factor. The current study used change in ambient light level on RTCs to investigate those situations where improved vision is likely to have significant impact, and therefore the situations where road lighting is of better cost-benefit effectiveness. For both motorcyclist and pedestrian RTCs there was a significant increase in overall RTC risk in darkness compared to daylight, indicating that there may be an overall benefit of road lighting. While darkness was a particular detriment at junctions for motorcyclists and on high-speed roads for pedestrians, road lighting may not be effective mitigation in either case and therefore alternative ways of increasing conspicuity should be considered.

HOW TO TAKE INTO ACCOUNT THE HETEROGENEITY OF OPTICAL PROPERTIES OF A PAVEMENT IN LIGHTING DESIGN?

Optimising lighting installations reduces energy consumption and stray light while providing optimal visibility conditions for road users. However, the origin of the large discrepancies often observed between the design of lighting installations and their actual performance remains poorly explained. For the design stage, it is assumed that the road has homogeneous photometric characteristics. To examine the impact of pavement heterogeneity on these differences, numerous measurements of pavement reflection properties were carried out on an experimental site with a portable device. A homemade software was used to perform several road lighting calculations by integrating the measured r-tables in different ways. New metrics based on lighting performance criteria deviation and pavement reflection properties deviation are used to compare the calculations. The results highlight the importance of measuring the optical properties of pavements and confirm methodological guidelines for making representative on-site measurements.

INFLUENCE OF ROAD SURFACES ON THE CALCULATION OF A TARGET VISIBILITY TAKING INTO ACCOUNT THE DIRECT AND INDIRECT LIGHTING

Street lighting ensures visibility and legibility for road users. In this paper, performances of the lighting installation of four road sections with different type of road surface are simulated in accordance with guidelines and road lighting standards. Then, the calculation of the visibility level of a target according to the Adrian’s model is included. Next, the light reflections on the road surface are added to the calculation of the target luminance. For this, the area considered in front of the target as well as the number of elementary surfaces are fixed and a Q_0-scaling of the r-table obtained for α=45° is performed. We compare the results obtained for each section with and without considering the light reflections and conclude that there is negligible incidence of the nature of the road surface on the target luminance. However, an effect of the road surface on the visibility level of the target is observed.

ILLUMINANCE AT THE EYE AS A SIMPLE METRIC FOR DISCOMFORT GLARE FROM PEDESTRIAN SCALE LUMINAIRES

In outdoor environments after dark, pedestrians may experience discomfort from road lighting. Previous studies have therefore developed models to predict discomfort from glare in pedestrian applications. However, the performance of these models has not been comprehensively assessed, and measurement challenges arise in field evaluations. This paper evaluates the performance of a model proposed by Bullough et al (2008) and compares it to prediction using only direct illuminance at the eye. Diagnostic metric tests were conducted using three independent datasets from previously published studies. The results suggested that direct illuminance at the eye performed similarly to the Bullough et al. model over the range of lighting conditions examined. These conditions included one glare source that contributed between 4 lx - 82 lx, and a low contribution from indirect illuminance and other lighting installations 1 lx - 4 lx. Further studies are needed to examine the importance of incorporating indirect illuminance from source and ambient illuminance for predicting discomfort glare.

A HOLISTIC METHOD FOR THE COMMISSIONING AND OPTIMISATION OF ADAPTIVE ROAD LIGHTING SYSTEMS USING LABORATORY AND FIELD MEASUREMENTS

This paper presents a set of field measurements performed at renovated lighting installations equipped with adaptive road lighting systems. The results revealed issues of over-illumination but also insufficient lighting levels that would not be shown without the field measurements. Since the adaptive road lighting systems can regulate the lighting output and should in parallel ensure adequate lighting and safety levels, the commissioning of such system is challenging. In this scope, we are proposing a holistic scheme for the commissioning and optimization of the operation of Adaptive Road Lighting systems taking into account field measurements, technical parameters of the incorporated equipment, and all aspects that may affect its performance. The proposed scheme can be used as a masterplan from the conception of the road lighting up to the validation field measurements and the long-term optimization and maintenance schedule of the installation.

OPTIMISATION OF A MOBILE METHOD FOR MEASURING ROAD LIGHTING CHARACTERISTICS (LUMINANCE AND ILLUMINANCE)

In today's urban environment it is extremely difficult to perform road lighting measurements using standard stationary methods. The mobile measurement method remains, in fact, the only possible way of assessing the quality of outdoor lighting. The presented work is aimed at improving the existing measurement methods in terms of quality, speed of measurement and safety of personnel.