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32 CHAPTER 5 Conclusions and Suggested Research To provide empirical evidence upon which to base guide- surement values. Therefore, measurement techniques for the lines for the selection and application of warning lights on lighting systems need to be standardized. A standard method maintenance vehicles, numerous light sources were examined has been developed at NIST as part of this project. The use of in three experiments: standardized lighting intensity measurement methods must be enforced in the lighting specifications from the state DOTs. It 1. A static screening experiment in which 41 light sources is recommended that the Form Factor method be specified were evaluated for conspicuity (attention-getting), glare, for reporting measurement from manufacturers (although the peripheral detection, and recognition. The light sources results proved to be very similar between all of the measure- varied by color, flash pattern, flash frequency, light type, ment methods). and placement on the vehicle, and were tested in varying The guidelines include the technical information necessary conditions of ambient light (day vs. night) and contrast for developing procurement specifications. The guidelines are lighting. presented in terms of the specific lights tested; however, the 2. A dynamic performance experiment in which the best three guidelines conclude with a section describing relevant charac- lights as determined from the static screening experiment teristics of these lights so that purchasing decisions can be made were used in an experiment conducted on a test track. One without reference to the specific lights tested here. In other light was used in two different positions, thus resulting in words, lights with characteristics similar to those tested here four lighting configurations. All the tested lights were amber should provide similar results. The guidelines are provided as (the color was chosen based on the results of the static an attachment to this report. screening experiment). The dynamic experiment included a surprise presentation in a visually complex environment, Considerations for Future Research followed by a series of tests under controlled ambient light- ing and weather conditions. The dynamic performance The lighting systems tested in this experiment were those experiments evaluated the four lighting configurations generally used for maintenance vehicles, and only pairs of in varying weather, distance, ambient light, and contrast lights with matching characteristics were tested. Advanced lighting conditions, using measures such as pedestrian de- lighting systems such as flashing bars and directional appar- tection distance, attention-getting, and discomfort glare, ent motion systems were not tested and should be considered among others. in future research. 3. A photometric characterization (stringent measurements of The test environment for the lighting systems used in this the light characteristics in a laboratory setting). research was a rural road; limited testing was conducted in a semi-urban environment. The initial testing indicated The results of each of the experiments were integrated into that a higher effective-intensity value may be required in guidelines for the lighting of service vehicles. an environment with roadway lighting and many other vehicles. Further research may be required to establish the impact of a more urban and visually complex environment Conclusions on the lighting requirements. Research found that several performance claims made by This research considered one vehicle color. The inte- manufacturers of lighting systems may not reflect true mea- gration of the lighting and the vehicle color may be sig-

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33 nificant; alternative colors should be considered in future could not be determined. Research addressing these factors research. should be considered. This research only considered rear approaches to a mainte- Research may be required to further investigate the rela- nance vehicle. Side and front approaches were not investi- tive importance of the dependent variables evaluated in gated, and the impact of the maintenance-vehicle headlamps this research.