Recommended CitationBischoff, A. L., and D. M. Bullock. Sign Retroreflectivity Study. Publication FHWA/IN/JTRP-2002/22. Joint Transportation Research Program, Indiana Department of Transportation and Purdue University, West Lafayette, Indiana, 2002. https://doi.org/10.5703/1288284313313
Signing is a big yearly cost to state DOT’s in sign maintenance and replacement costs. In 2001 the Indiana Department of Transportation (INDOT) replaced 14,930 signs at a cost of $1,067,931 and did maintenance work on 34,084 signs at a cost of $2,136,076. Recently, guidelines have been proposed by the Federal Highway Administration (FHWA) for minimum retroreflectivity of traffic signs for state, county, and city roads in the United States. The purpose of this study was to evaluate if the majority of the signs currently used by INDOT will meet the new minimum requirements proposed by the FHWA. In addition, this study provides quantitative data to assess the effectiveness of the current sign replacement program used by the Indiana Department of Transportation (INDOT) and determine if the current ten year replacement schedule is adequate to keep the State of Indiana in compliance with the new guidelines or if adjustments need to be made. This study was limited to ASTM Type III sheeting. The data analysis performed on the data collected from the field showed the vast majority of the signs are expected to meet the proposed retroreflectivity minimums with no change in the current 10 year replacement policy. Over 98% of the signs in the field under normal circumstances should not only meet but exceed the proposed retroreflectivity minimums for any speed or size sign. It is recommended that the life cycle of traffic signs with white and yellow backgrounds can be safely extended for at least two years to 12 years, providing there are is no apparent damage or defects. Red, however, should not be left out in the field for longer than 10 years because the red coloring at that point has faded too much. Such a policy could save INDOT at least $27,000/year in material costs.
Retroreflectivity, Sign, Sheeting, Visibility, Deterioration, SPR-2482
Joint Transportation Research Program
West Lafayette, IN
Date of this Version