Doctoral Dissertations

Date of Award

8-1995

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Engineering Science

Major Professor

John C. Hungerford

Abstract

The purpose of this study was to develop guidelines and recommendations for the design of retroreflective marking systems to enhance the conspicuity of rail cars at night. Specifically, the research provided human performance data that can be used to design marking systems for any large object that needs to be detected by motorists in a low contrast environment. Three methods were used generate and evaluate marking systems that were believed capable of enhancing rail car conspicuity. First, a group of human factors and transpor-tation engineers used the Nominal Group Technique to generate 10 retroreflective rail car marking systems, three of which were based on designs that are currently used on rail cars or highway trucks. A rail car with standard nonretroreflective Association of American Railroads (AAR) markings was included as the eleventh system to provide a comparative baseline. Secondly, two panels, one comprised of individuals with expertise in the area of conspicuity markings and one without this expertise, made subjective judgments as to the effectiveness of the 11 marking systems. Finally, a computer controlled real-time experiment, utilizing color slides of marking systems that were designed based on the results of the subjective evaluation, was conducted to establish detection and recognition times and distances. The subjective evaluation suggested that fluorescent yellow or red-white color patterns that outlined the shape of the rail car or distributed the markings over a relatively large area of the car side were the most effective retroreflective marking systems. This evaluation also suggested that, regardless of the distribution pattern, an all red color pattern would be the least effective color pattern for a retroreflective marking system. Likewise, the evaluation suggested that, regardless of the color pattern, a distribution pattern which concentrated the marking system along the side sill of the rail car would be the least effective distribution pattern for a retroreflective marking system. The subjective evaluation indicated that any retroreflective marking system was superior to the standard AAR markings. As in the subjective evaluation, all of the retroreflective systems tested in the objective evaluation performed well when compared to the standard AAR markings. The data indicated that bright color patterns distributed to give an indication of the size or shape of the rail car make the most effective marking systems for both detection and recognition. For detection the fluorescent yellow color pattern was the most effective color pattern regardless of the distribution pattern. However, for recognition, fluorescent yellow or red, that is color patterns of a single color, were equally effective; and either were more effective than a color pattern made up of red and white. As in the subjective evaluation, distribution patterns that concentrated the marking system along the side sill were the least effective regardless of the color pattern. Based on the results obtained from the subjective and objective evaluations, the following conclusions were reached:

1. Retroreflective marking systems were much more effective than standard white paint reporting marks done to AAR standards.

2. The interaction of color pattern and distribution pattern contributed more to the effectiveness of the marking systems than did either the color pattern or the distribution pattern alone.

3. Distribution patterns that outlined the sh^e or that spaced the retroreflective material over a relatively large area of the freight car side were superior to distribution patterns that concentrated the retroreflective material along the bottom of the car.

4. At long distances, reflectivity appeared to be more important than the color used for the color pattern.

5. For nighttime effectiveness, a high contrast ratio between a single color pattern and the background performed better than did a color pattern of two contrast-ing retroreflective colors against the same background.

6. For the fixed amount of retroreflective material used in this research, a single color pattern with a high coefficient of retoreflection was more effective than a 60-40 ratio contrasting two color pattern (e.g., red|white) with a combined smaller coefficient of retroreflection.

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