A comparative analysis of trade-off between size and retroreflectivity of traffic signs.

摘要

The objective of this study is to determine how changes in sign size and luminance affects driver's ability to find and read traffic signs during day and night conditions.; This research attempts to answer the following questions: (a) What is the effect of sign size and/or brightness in detection of the traffic sign? (b) Does driving age have a disproportionate effect on the legibility readings when sign and/or brightness is changed? (c) Do size (3-levels) and brightness (2-levels) have an effect on driver expectation of detecting traffic signs? (d) Does type III sheeting have greater adverse effects on the legibility distance than type II sheeting?; This research used standard traffic signs with letter series D. The analyzed factors were: (1) age, at two levels (20–30 and above 65), (2) sign size or size of sign legend, (3) difficulty of sign legend, (4) background material at two levels (types II and III) and (5) two levels of driving conditions (night and daytime). The purpose of this grouping was to determine if driver age had an effect on the legibility distances during day and nighttime driving. Daytime and nighttime were the background luminance of the study.; A questionnaire was distributed to the subjects to get information on personal experience using traffic signs. The subject's response is simulated with actual observation to relate personal subjective driving experiments with actual distance for detecting and understanding the message conveyed by the signs.; Cost models were recommended to estimate the overall costs of different alternatives, based on upgrading sheeting materials or the sign size. The implementation and the overall cost impacts and selection of an alternative (i.e., engineering type II grade and Hi-Intensity sheeting) shall be on each state and local authority. The most natural alternative is for the authorities to indicate the dense areas or locations that mostly will benefit from larger and brighter signs. This will allow the drivers to benefit from upgraded signage, and the state or local authority is not under financial burden to replace all the signs under their jurisdiction. The signage improvements will empower the older drivers to understand and detect the traffic signs in less time. It is suspected that sign improvements should have a direct effect on the accident rates in the short-term and improving roadway safety in the future.