CHAPTER 1

Introduction

Roadway lighting must balance user needs and safety with the impact of the lighting system on the environment. There are six factors to consider in the application of roadway lighting: (1) user safety; (2) energy efficiency; (3) impacts on humans, both on the roadway and surrounding the roadway; (4) impacts on the environment; (5) impacts on sky glow; and (6) user perception. The importance of each of these factors varies based on the application. As an example, the impact of lighting on flora and fauna might be considered as more important for a roadway along a wildlife reserve or in a coastal region, whereas user safety might be more critical on interstates and major arterials. Unlike any other time in the history of roadway lighting, the balance between all these factors is now achievable with the instant-on and dimming capabilities of solid-state lighting (SSL) systems along with the utilization of controls.

Many of the above factors have been extensively studied, with study outputs including the development of metrics for some factors, which can be considered when selecting lighting for different applications. User safety was one of the primary focuses of NCHRP 05-22: Guidelines for Solid-State Roadway Lighting, which identified considerations for visibility in the area around the roadway as part of the surround ratio along with the uniformity of lighting on the roadway. NCHRP 05-22 also considered the application needs of SSL in terms of the technical approach for lighting design. However, as discussed in the report, significant gaps remain as to how these technologies are applied from a design standpoint. Thus, further research is required to develop recommended practices that lighting designers can apply to achieve complete balance between user safety and environmental impacts.

Goal

The goal of this research was to fill the gaps in knowledge related to the further application of SSL to roadways. Building on the safety-focused efforts of NCHRP 05-22, this project will identify further tools and solutions to fill in the knowledge gaps associated with the application of lighting technology, with an eye to present day and the needs of the future. The focus areas of the project will include automation and intelligent transportation system (ITS) integration, crash modification factors (CMFs) in lighting, and the impacts on flora and fauna,.

Research Approach

During this project, four fundamental questions arose:

1. What are the present and future impacts of automation and connectivity on roadway lighting?
2. What are the infrastructure needs associated with connecting lighting and ITS frameworks?
3. What are the CMFs for roadway lighting based on geometry type, road conditions, and atmospheric conditions?
4. What are the best metrics to evaluate the effects of roadway lighting on flora and fauna, and what are the limitations?

In response to these questions, the project was divided into three significant efforts, each considering three different aspects of the application of lighting to the roadway. These three efforts considered (1) the needs of lighting within the ever evolving ITS network, (2) the application of CMFs for roadways, and (3) the characterization of the effects of roadway lighting on flora and fauna. Each one of these efforts was performed independently within the overall project.

Report Format

As the project was performed in three separate tracks, a separate report was written for each of these efforts and each is included here as Appendices to this report (Appendix A, Appendix B, and Appendix C). The combined report provides a summary of the research effort and considers the results and conclusions of each individual effort.

Lighting Automation and the ITS Framework

This portion of the report (Appendix A) began with a literature review focusing on domestic and international sources to synthesize the current state of knowledge in the areas of connected/automated vehicle (CAV) sensors and their interactions with ambient lighting and weather, road lighting needs for CAVs, and communication protocols between CAVs and infrastructure as they relate to lighting. Following this, an experiment was performed that evaluated the performance of a vehicle automation system in detecting a pedestrian under varying lighting levels. Finally, a review of the status of automation in the field is provided.

CMFs for Solid-State Roadway Lighting Applications.

This portion of the report (Appendix B) focused on the process of developing CMFs and provided guidelines for the development of CMFs in lighting with an example calculation. Attention was paid to data requirements of the CMFs. The calculation and the result are shown in this document.

Characterization of the Effects of Roadway Lighting on Fauna and Flora

This final portion of the project (Appendix C) focused on the spectral and lighting intensity response of plants and animals in a roadway setting. The literature review included investigation of the impact of lighting on flora and fauna, limits for where effects are no longer critical, and any actinic functions developed for any species and plant life. A research effort was undertaken to develop a metric that compares the impact of a given lighting design on a species to that of the moon on the same species.