Roadway Lighting

This article provides an overview of the engineering considerations for designing an effective roadway lighting system, as well as the requirements for maintaining the system and the nuances of determining responsibility for roadway lighting systems that have been inadequately maintained.

Roadway Lighting Design & Maintenance

Design of roadway lighting is based upon a number of factors including the size of the roadway, the anticipated volume of vehicle and pedestrian traffic, and the anticipated speeds at which vehicles will travel. What is reasonable for limited access freeways will be different than what is reasonable for residential streets with crosswalks. The facts of each incident are relevant to determining if deficient lighting created a hazard.

The science of lighting is known as “photometrics.” From a photometric standpoint, the performance of roadway lighting is defined in terms of how intense the lighting is, which is measured in foot-candles or lux, and uniformity, which is measured as ratio of the average intensity to the minimum intensity.

Roadway lighting must be intense enough to allow drivers and pedestrians to recognize potential hazards, and lighting must be uniform enough that the iris of the human eye does not constantly need to expand and contract.

A third consideration of lighting design is glare, which is light shining directly into the eye; it is more difficult to see when one is having to squint due to being overwhelmed by bright lights.

Each of these factors can be calculated by photometric software. The results of the software’s calculations are based upon real-world conditions and data provided by lighting manufacturers. Results are plotted as a grid of points across the roadway and are accompanied by tables listing the ranges and averages of the calculated points.

Roadway Lighting Maintenance

The maintenance of roadway lighting is essential. There is no benefit to placing lights along a roadway if they are not functioning. Light fixtures, also known as luminaires, have a finite life. A luminaire will produce less light over time and could eventually fail to meet the needs of the roadway. Light degradation is a predictable factor and regular maintenance is required.

Maintenance of roadway lighting is required to keep the power on and to repair or replace defective components. Power can be lost due to weather events or during the construction and maintenance of the power system itself.

Components which can fail include sensors, lamps, lamp ballasts, LED drivers, and electrical connections such as sockets and wiring. Managing the maintenance of roadway lighting includes periodic inspections and timely responses to problems reported by inspectors, first responders, and the public.

Responsible Parties in Roadway Lighting Disputes

Determining the party who is responsible for maintenance of a roadway lighting system can be complex as it may involve some combination of local/state government, utility companies, and contractors.

At times, a third party may be responsible for the lighting system for a specific duration. An instance of this arrangement would be a general contractor performing construction on an existing roadway.

Between the system’s owner, the general contractor, the subcontractors, and the utility company, attributing responsibility can be a challenge. The determination of responsibility is based upon an examination of contracts, records, and standards.

To parse through the facts and data, an expert must be knowledgeable of lighting design as well as the construction and operation of power systems, the operation and maintenance of lighting systems, the science of luminaire components, and relevant standards.

Roadway Lighting Expert Witness Investigations

The electrical engineering experts at Robson Forensic have extensive experience and knowledge of roadway lighting systems; our engineers have designed roadway lighting systems from the ground up, they have worked with utility companies to install and maintain luminaires, and they have the ability to perform lighting studies to assess whether the lighting conditions surrounding your matter were reasonable.

For more information, submit an inquiry or call 800.813.6736.

Featured Expert

Peter J. Ford, P.E.

Electrical Engineer & Electrical Systems Expert

Peter Ford is a licensed electrical engineer with more than a decade of professional experience in design, management, and consulting. He applies his expertise to forensic casework involving… read more.