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5 CHAPTER 1 Introduction and Research Approach Background 1. Collection and review of relevant literature, specifications and guidelines, research findings, current practices, gov- Roadway operations equipment used for construction, ernment requirements, and other information relative to maintenance, utility work, and other similar activities gener- selection and application of warning lights on equipment ally operate within the roadway right-of-way. These vehicles used in roadway operations. Motorist response and other and mobile equipment operate on all types of roadways, during criteria used in the selection process were also identified and daytime and nighttime hours, and under all weather condi- discussed. This information was assembled from published tions. To improve motorist and work-crew safety, equipment and unpublished reports, contacts with transportation agen- must be readily seen and recognized; therefore, warning lights cies and industry organizations, and other domestic and are provided on the equipment to alert motorists of poten- foreign sources. tially hazardous situations. Amber warning lights have tradi- 2. Identification and discussion of the factors related to the tionally been used, although lights of other colors are often design and selection of warning lights. These factors in- added with the intent of helping the traveling public better see cluded type and purpose of vehicle; daytime and night- the equipment. Combinations of amber, blue, and white lights time operations; weather conditions (e.g., snow, rain, fog, and other forms of warning lights (e.g., lighted bars, lighted and dust); light details (e.g., color, type of light source, con- "arrow sticks," strobes, light emitting diodes [LED], and alter- figuration and effective intensity of lights, flash patterns and nating flashes) are used. There is a concern that this variety of parameters, location of lights on vehicles, and durability); lighting on roadway operations equipment has evolved with- color of the vehicle and markings on it; and distinguish- out adequate consideration of the effects on the awareness ability from emergency response vehicles. and responsiveness of motorists. 3. Assessment of the relevance and importance of the identi- There are no widely accepted guidelines for selecting warn- fied factors to the selection and application of an effective ing lights on roadway operations equipment that consider the lighting system, development of a prioritized list of these type of equipment, weather conditions, daytime and nighttime factors, and recommendation of specific factors for further operation, color of vehicle, or other relevant factors. Research research. was needed to develop guidelines for use by transportation 4. Preparation of a detailed work plan that included exper- agency personnel in selecting and procuring lights that will sub- imental investigations for addressing the recommended stantially enhance motorist awareness. NCHRP Project 13-02 factors and developing the guidelines. was conducted to address this need. 5. Conduct of the recommended investigations and develop- ment and validation of the guidelines for the selection and application of warning lights on vehicles and mobile equip- Objective ment used in roadway operations. The guidelines also in- The objective of this research was to develop guidelines for cluded the technical information necessary for developing selection and application of warning lights to improve the con- procurement specifications. This task was composed of the spicuity and recognizability of roadway operations equipment photometric evaluation of the light sources, and static and (i.e., vehicles and mobile equipment) used for construction, dynamic human factors tests. maintenance, utility work, and other similar activities. This 6. Submittal of a final report that documented the entire objective was accomplished through the following tasks: research effort.