Traffic signs communicate important information to drivers. In real situations, such as driving fast and traveling at night, drivers have limited time to read and understand signs.
At night, highly retroreflective sheeting helps make traffic signs more conspicuous and easier to read. Research shows that the use of higher performing reflective sheeting—resulting in brighter, more visible signs—helps reduce crashes and has a positive cost-to-benefit ratio.1
A study consisting of a systematic upgrade of 2,400 traffic signs among nearly 11,000 signs in Mendocino County, CA showcases the overall cost-to-benefit ratio of the upgrades that were made. Crashes in rural county-maintained roadways were analyzed for three-year periods before and after the upgrades.3
On the roadways where signing and marking upgrades were made, there were significant decreases in crashes that resulted in reduced property damage (reduced by 42%), injuries (reduced by 42%) and fatalities (reduced by 61%). A total upgrade program cost of $79,260 resulted in total savings of an estimated $12,580,000. The resulting return on investment was 159:13.
It is important to note that multiple factors, such as seasonal variations, and changes in traffic patterns and volumes make it difficult to run a “controlled experiment.” It is difficult to attribute any variations in crash rates to a single factor such as traffic sign upgrades.
Recently, the city of Albuquerque, New Mexico upgraded its traffic signs in multiple sections of the city. These sections were upgraded with retroreflective sheeting that complies with ASTM D4956 Type XI. Other segments of the city were designated as controlled segments.
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The researchers also noted a decreased in the nighttime fatal injury crashes in the treatment segments replaced with signs upgraded to ASTM D456 Type XI-compliant retroreflective sign sheeting. No such decrease was observed in the control segments.
The improvement in the information transfer speed of brighter signs might help explain this safety improvement. Researchers suggest that brighter signs allow drivers to obtain information quickly and/or more accurately. Such signs can help provide a more conspicuous target to nighttime drivers, especially when scene complexity increases.2
Research suggests that traffic signs with optimal levels of luminance offer immediate safety benefits for agencies and motorists. Brighter signs can be a simple and actionable safety improvement. See the difference between High Intensity Prismatic and Diamond Grade™ reflective sheeting.
1 Ripley, D.A., Howard R. Green Company, ITE AB04H313, Quantifying the Safety Benefits of Traffic Control Devices—Benefit-Cost Analysis of Traffic Sign Upgrades, 2005. Contact 3M for the full report.
2 Schnell, T., Yekhshaytan, L., Daiker, R., Konz, J., Effect of Luminance on Information Acquisition Time and Accuracy from Traffic Signs, Operator Performance Laboratory, University of Iowa, 2008. Contact 3M for the full report.
3 Ford, S. H. (2003). Evaluation of Low Cost Program of Road System Traffic Safety Reviews for County Highways. Journal of the Transportation Research Board, LVR8-1048. Contact 3M for the full report.