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The National Academies

NCHRP 05-26 [Anticipated]

Development of an Updated Warranting System for Roadway Lighting

  Project Data
Source: AASHTO Technical Committee on Roadway Lighting and Delaware Department of Transportation
Funds: $350,000
Staff Responsibility: Christopher T. McKenney
Fiscal Year: 2023

This project has been tentatively selected and a project statement (request for proposals) is expected to be available on this website. The problem statement below will be the starting point for a panel of experts to develop the project statement.

Many state and local departments of transportation (DOTs) and safety practitioners use warranting to define the need for lighting. Currently there are two main warranting systems for roadway lighting: one is in the AASHTO Roadway Lighting Design Guide that defines lighting warrants for freeways and highways, and the other in The Transportation Association of Canada (TAC) Guide for the Design of Roadway Lighting that defines warranting for streets, highways, freeways, and intersections. The majority of the warranting in TAC is based on a weighted point score system developed in the 1970s and derived from an early 1970s NCHRP research and the late 1970s FHWA Federal Highways Lighting Handbook. The AASHTO warranting system was developed in the early 1980s and has not changed significantly since then. Although the AASHTO and TAC publications are relatively current, the warranting system contained within them has not been updated in at least 30 years.

The existing warrants for lighting were developed before the recent development of active safety systems in vehicles, solid-state lighting, and the implementation of the use of crash modification factors (CMFs) in roadway safety analysis. With the advancement of applications of LED lighting system for new or replacement of existing lighting fixtures, there is a significant requirement to create new data associated with the need for new lighting. In addition, warrants do not address safety-based alternatives to roadway lighting, which include retroreflective pavement marking and roadside delineators. There is also growing pressure to reduce potential environmental impacts of roadway lighting. Jurisdictions often must balance the safety benefits of roadway lighting while aiming to reduce potential environmental impacts, such as energy use and impacts to wildlife.

Roadway lighting also can be expensive to install and operate. Over-lit and unwarranted lighting luminaires can result in excessive glare, lighting trespass in the adjoining neighborhood, and sky glow. Additionally, current warranting systems do not address the cost-benefit of roadway lighting as a safety measure compared to other safety alternatives, resulting in inconsistency as to where and when roadway lighting is applied. Therefore, research is needed to develop appropriate CMFs for state-of-the-art lighting system as most state and local DOTs are relying on CMF to justify the safety benefits of installing roadway lighting.

The objective of this research is to develop an updated warranting system that (1) provides linkages to CMFs, and (2) assess roadway lighting compared to other roadway safety treatments and consider the safety impacts on modern vehicle technology and new lighting technologies. The goal would be to develop a system that is easy to use and creates consistency with respect to how roadway lighting is applied as a safety countermeasure. In addition, other safety measure frameworks to access the benefit of roadway lighting to other road safety measures also would be discussed.

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