Highway construction safety and the aging driver: Detection and legibility distances of construction warning signs

With the number of elderly drivers increasing, means of improving signage visibility and legibility must be developed to improve highway safety for all drivers. This urgent need is especially true in regard to hazardous or unfamiliar traffic situations such as construction work zones.;In order to meet these objectives, four research procedures were conducted: an extensive literature review, vision screening, a real-world field experiment, and an accelerated weathering test of FODG, SEG, and HI sheeting materials in conjunction with the Arizona Department of Transportation. In addition, contact was made with numerous researchers in the field. The basis for the findings and conclusions of this study resulted from these activities.;This study examines the effects of highway warning sign size and brightness of sheeting material variations upon detection distance (the point at which an individual becomes aware that a specific sign exists) and legibility distance (the point at which a sign's information is processed and understood), as experienced by certain drivers: a young control group and a mature target group.;Fluorescent Orange Diamond Grade has the highest target value of the three sheeting grades, making it the most desirable in terms of visibility and legibility. However, FODG's color began to fail after only one year. HI outperformed SEG in terms of detection distance, while the two materials were nearly identical with regards to daytime legibility distance, with the mean distance for SEG slightly higher than that of HI during nighttime legibility testing.;The overall objectives of this project are fourfold: (1) To investigate the effect of sign size and SIA (brightness) on the visibility and legibility of construction work zone traffic signs; (2) To determine the best combination of sign size and retroreflective sheeting material in terms of providing maximum visibility and legibility for elderly drivers; (3) To evaluate the effects of the new Fluorescent Orange Diamond Grade (FODG) material on driver performance within construction zones--as compared to the effect of Super Engineering Grade (SEG) and High Intensity (HI) sheeting materials; (4) To evaluate the relative sheeting material longevity for use on construction work zone traffic signs of Fluorescent Orange Diamond Grade, Super Engineering Grade, and High Intensity grade sheetings.;SEG has been found to be more desirable for construction zone usage than HI because SEG causes less glare, provides considerably less cost and involves less problems with handling and fabrication.;Sign sizes used in the study include 30" x 30", 36" x 36", and 48" x 48". It was found that the 36" x 36" was the most effective, as increasing sign size increases legibility only to a certain point; beyond a 36" x 36" sign the legibility increase is negligible. The overall cost for the large 48" x 48" sign is relatively excessive, therefore unjustified.