How can brighter
signs help improve road safety?
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
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
What is the
cost-to-benefit ratio to upgrading road signs?
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
Can upgrading road
signs reduce car crashes?
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
Read a synopsis of these studies and learn more about:
ASTM D4956 Type XI – compliant sheeting can improve nighttime safety
luminance needs for optimal sign legibility
information acquisition time
luminance and the effect on safety
The researchers noted a decrease in
the nighttime fatal injury crashes in segments upgraded to ASTM D4956
Type XI-compliant retroreflective sign sheeting. No such decrease was
observed in the control segments.
Less Time Reading,
More Time Driving
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.