Selecting the Optimal Sheeting-Font Combination to Increase the Visibility of Roadway Guide Signs in the Presence of Glare

摘要

Background: Driver safety remains an important issue, and improving roadway guide sign visibility is an important step in increasing safety on roadways and thus reducing crashes. Currently, two types of retroreflective sheeting materials (type IV and type XI) and either Series E (Modified) or ClearviewHwy font types are used for signs in the United States. Glare from an oncoming vehicle's low beam headlights, however, can create visual difficulty for drivers at night. Purpose: The purpose of this study was to evaluate the performance of two retroreflective sheeting materials and two font types, for use on shoulder-mounted guide signs (i.e., mounted on the shoulder of a roadway) in the presence of glare. Methods: Four sheeting-font combinations, involving type IV and type XI sheeting materials and Series E (Modified) and ClearviewHwy fonts were compared in a field experiment. Participants were asked to read the legend of four signs during nighttime driving, in the presence of glare from an oncoming low beam headlight vehicle. The legibility distance at which the participant read the sign was recorded as the dependent variable. A cost comparison was also performed for the four signs. Results: Type XI sheeting combined with ClearviewHwy font provided the maximum legibility distance. The cost analysis showed that type XI was less expensive over a 60-year timeframe (～9.3% lower) versus type IV. Conclusions: Use of type XI sheeting and ClearviewHwy font is recommended for shoulder-mounted roadway signs to enhance legibility. However, future work is needed to verify these results under more general conditions and with a broader range of participants.