The need to see traffic signs at night has led to the development of increasingly brighter retroreflective sign sheeting. The impact of this increased brightness has been shown to increase the legibility distance of the sign, but at what cost? With brighter signs being visible from farther away, there is an increased opportunity for the driver to look at the sign. This thesis assesses the impact of sign brightness on the nighttime driverAcA?A?s sign viewing behavior; such as the number of glances and the total glance duration directed at the sign. Eye-tracking technology has been used to follow the nighttime driverAcA?A?s eye movements through tasks based on sign usage. The six signs used for the analysis are classified in three relative brightness categories of bright, medium, and dim on a closed course and on a public road. Data relating to the beginning and end of each glance were recorded as well as the distance at which the sign became legible to the driver. Comparisons were made between the three brightness levels for the number of glances, total glance duration, and legibility distance of the sign. Further analysis was conducted to determine the effect of the testing environment on a driverAcA?A?s sign viewing behavior by comparing the results from the closed course with those from the open road. The data for this thesis show varying results between the two courses with more defined differences based on luminance for the open road. The results of this thesis indicate that drivers do not consistently change the number of times they look at a sign or the amount of time dedicated to a sign based on its brightness. During real world driving scenarios, the brightest sign resulted in the longest legibility distance and the lowest total glance duration, indicating an increased efficiency reading the sign by the driver. Typically, a sign with a longer total glance duration had a shorter legibility distance. Comparisons between the closed and open courses revealed that open road driving resulted in a longer total glance duration and a shorter legibility distance.
