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 driverâÂÂs 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 driverâÂÂs 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 driverâÂÂs 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
