2.1 Determination of Lighting Need

The FHWA review process requires a warrant analysis, project criteria document, maintenance plan, and MOU

The FHWA administers funding for State roadway lighting projects that meet certain requirements in terms of need. These projects are eligible under Section 148 of Title 23, United States Code (Highway Safety Improvement Program). In addition, these projects are eligible for the increased Federal share under 23 U.S.C. 120(c).

When Federal aid is used for a lighting project, the applicant can support the need for a roadway lighting system by including the following items:

• A warrant analysis showing that lighting is a warranted safety feature.
• A project criteria document showing that the design criteria established by AASHTO or the IES will be used and met as part of the design.

A safety analysis and study showing that a lighting system is a cost-effective safety alternative for the project may also be considered. There are various ways of executing a study of this type. One is to use the AASHTO Highway Safety Manual – 2010 (HSM)(25). The HSM has assembled currently available information on crash frequency and severity so that various improvements to roadways could be quantified and evaluated in terms of their effectiveness. Some of the effects of various treatments, such as geometric improvements or operational changes on roadways, are quantified as Crash Modification Factors (CMFs). CMFs represent the change expected in crash frequency due to a specific change in conditions.

For example, in looking at the impact of highway lighting on all roadway types that previously had no lighting, for nighttime injury crashes, the HSM reports that research has shown a resultant CMF of 0.72 (showing that there would be a reduction of 28 percent in nighttime injury crash types). So if the expected average crash frequency is 10 injury crashes/year for a no-lighting condition, then after implementation of a highway lighting system one would expect 10 X 0.72 CMF = 7.2 injury crashes/year.

The amount of information for crash analysis and evaluation is actively growing and can be found at the Crash Modification Factors Clearinghouse at www.cmfclearinghouse.org. In this clearinghouse the viewer can sort through data by the type of countermeasure, crash type, crash severity, and roadway type. The viewer can also see a measure of accuracy and precision of the data, as well as applicability, as judged by a panel of reviewers, and rated with a system using a 1-5 star scale.

Figure 2 - Example of Data from the Crash Modification Factors Clearinghouse

2.2 Determination of System Maintenance

FHWA requires that federally funded lighting systems be adequately maintained. The Federal Regulations (23 CFR 1.27) state "The responsibility imposed upon the State highway department, pursuant to 23 U.S.C. 116, for the maintenance of projects shall be carried out in accordance with policies and procedures issued by the Administrator. The State highway department may provide for such maintenance by formal agreement with any adequately equipped county, municipality or other governmental instrumentality, but such an agreement shall not relieve the State highway department of its responsibility for such maintenance."

2.3 Design for Older Drivers

The FHWA has prepared a Highway Design Handbook for Older Drivers and Pedestrians (9) that "provides practitioners with a practical information source that links older road user characteristics to highway design, operational, and traffic engineering recommendations by addressing specific roadway features." The handbook "supplements existing standards and guidelines in the areas of highway geometry, operations, and traffic control devices."

Included in the handbook are recommendations for fixed lighting installations at intersections and interchanges for the older driver. This handbook is not intended to constitute a new standard of required practice, but to provide a resource to practitioners and owners during the decision-making process.

The recommendations for intersections include the following:

Wherever feasible, fixed lighting installations are recommended as follows:

1. Where the potential for wrong-way movements is indicated through crash experience or engineering judgment.
2. Where twilight or nighttime pedestrian volumes are high.
3. Where shifting lane alignment, turn-only lane assignment, or a pavement-width transition forces a path-following adjustment at or near the intersection

The handbook also recommends regular cleaning of lamp lenses, and lamp replacement when output has degraded by 20 percent or more of peak performance (based on hours of service and manufacturer's specifications), for all fixed lighting installations at intersections.

The recommendations for interchanges state:

Complete interchange lighting (CIL) is the preferred practice, but where a CIL system in not feasible to implement, a partial interchange lighting (PIL) system comprised of two high-mast installations (e.g. 18- to 46-m- [60- to 150-ft-] high structures with 2 to 12 luminaires per structure) per ramp is recommended, with one fixture located on the inner ramp curve near the gore, and one fixture located on the outer curve of the ramp, midway through the controlling curvature.

2.4 Railroad Grade Crossings

The FHWA has a handbook (10) dealing with railroad-highway crossings that is meant to "provide a single reference document on prevalent and best practices as well as adopted standards relative to highway-rail grade crossings." The abstract states: "The handbook provides general information on highway-rail crossings; characteristics of the crossing environment and users; and the physical and operational improvements that can be made at highway-rail grade crossings to enhance the safety and operation of both highway and rail traffic over crossing intersections. Theguidelines and alternative improvements presented in this handbook are primarily those that have proved effective and are accepted nationwide."

The recommendations for lighting state:

"Illumination at a crossing may be effective in reducing nighttime crashes. Illuminating most crossings is technically feasible because more than 90 percent of all crossings have commercial power available. Illumination may be effective under the following conditions:

• Nighttime train operations.
• Low train speeds.
• Blockage of crossings for long periods at night.
• Crash history indicating that motorists often fail to detect trains or traffic control devices at night.
• Horizontal and/or vertical alignment of highway approach such that vehicle headlight beam does not fall on the train until the vehicle has passed the safe stopping distance.
• Long dark trains, such as unit coal trains.
• Restricted sight or stopping distance in rural areas.
• Humped crossings where oncoming vehicle headlights are visible under trains.
• Low ambient light levels.
• A highly reliable source of power.

Luminaires may provide a low-cost alternative to active traffic control devices on industrial or mine tracks where switching operations are carried out at night.

Luminaire supports should be placed in accordance with the principles in the Manual for Assessing Safety Hardware (MASH) and NCHRP Report 350.117. If they are placed in the clear zone on a high-speed road, they should be designed with a breakaway base."

2.5 Crosswalks

FHWA has prepared an informational report on crosswalk lighting (FHWA-HRT-08-053: Informational Report on Lighting Design for Midblock Crosswalks)(11). The report "provides information on lighting parameters and design criteria that should be considered when installing fixed roadway lighting for midblock crosswalks. The information is based on static and dynamic experiments of driver performance with regard to the detection of pedestrians and surrogates in midblock crosswalks. Experimental condition variables included lamp type (high-pressure sodium and metal halide), vertical illuminance level, color of pedestrian clothing, position of the pedestrians and surrogates in the crosswalk, and the presence of glare. Two additional lighting systems, a Probeam luminaire and ground-installed LEDs, were also evaluated. The research found that a vertical illuminance of 20 lx in the crosswalk, measured at a height of 1.5 m (5 ft) from the road surface, provided adequate detection distances in most circumstances. Although the research was constrained to midblock placements of crosswalks, the report includes a brief discussion of considerations in lighting crosswalks co-located with intersections."

The results of this report were included in the revised IES RP-8 Standard Practice for Roadway Lighting (29)

2.6 Roundabouts

FHWA has prepared and informational guide on the design of roundabouts (NCHRP Report No. 672 : Roundabouts: An Informational Guide – Second Edition)(31). In this document it states that illumination is recommended for all roundabouts, including those in rural environments, and gives other advice for mitigation if lighting cannot be provided. The document also includes typical lighting levels for approach roadways which are then summed to determine the roundabout lighting levels.