• Retroreflectivity: a guiding light for black spots

    road turn on dark road with yellow arrow signs and delineation

    • Retroreflectivity – increasing visibility for changing road conditions

      Driving at night can be difficult – especially on poorly lit rural roads with unexpected twists and turns.

      According to the U.S. Federal Highway Administration (FHWA), “… the majority of highway fatalities take place on rural roads.” with rural areas having a 2.4 times higher fatality rate than fatality rates in urban areas1”. Globally, the World Health Organization (WHO) notes in their Road traffic injuries fact sheet that “the lives of approximately 1.25 million people are cut short as a result of a road traffic crash.2

      Conditions that create these statistics may, in part, be addressed through retroreflective technology that helps to increase safety in high crash locations, also known as “black spots”.


    • Yellow arrow signs on road corner

      What are black spots?

      The FHWA defines black spots as “locations with the highest crash frequency …3”, similarly, the Queensland Government, Department of Transport and Main Roads refers to black spots as “…road locations that have a record of large numbers of crashes.4” India is more specific, defining black spots as “…a stretch of NH (500 m) or any other road with 5 or more road accidents or 10 fatalities occurring in the last 3 years.5

      Black spots occur in urban and rural areas. Consider this, you’re driving on a rural road and the road and area ahead seems to disappear. That is often considered a black spot. Unexpected sharp corners, hills, winding paths, hidden junctions and poor or concealed warning signs can all contribute to black spots. Without clear road direction, drivers are caught off guard by the changes in the road.

    • Rural road corner

      Keeping vehicles on the road

      As vehicles become more affordable in low- to middle-income countries, infrastructure and policies struggle to keep apace. Setting speed limits and classifying road designations depending on conditions like dangerous curves or mountainous regions may be limited at a local level.

      In Countermeasures to Keep Vehicles on Roadways6 the FHWA recommendations for preventing roadway departure, a problem that can be symptomatic of black spots, include:

      • Pavement friction like overlays, grooving and surfacing.
      • Rumble strips and rumble stripes for center line, edge line and shoulder.
      • Horizontal curve safety. (The Curve Safety Enhance Program was implemented in the state of Minnesota with countermeasures including center and edge lines, signage, and use of high retroreflectivity and fluorescence.)
      • Nighttime visibility with sign retroreflectivity, pavement markings and roadway lighting.

    • Why retroreflective technologies for black spots?

      Retroreflective sheeting and pavement marking technology is ideal for ensuring maximum reflectivity on dark roads. Advances in retroreflective sheeting have resulted in signage that reflects 58% of light back toward the driver – almost quadrupling road signs’ overall brightness from encapsulated glass beads that reflect 14% of light back to the source.

      A study presented at Mid-Continent Transportation Research Symposium Proceedings found that where more-visible signs are installed, crash numbers fell 25% to 46% in three to six years. In the study, Quantifying the Safety Benefits of Traffic Control Devices: Benefit-Cost Analysis of Traffic Sign Upgrades (PDF, 68.56 KB), the author, D.A. Ripley, indicated that “… a sign upgrade from engineer-grade to high-intensity (ASTM Type III) or Diamond Grade™ (ASTM Type IX) reflective sheeting could bring about improvement in safety while encouraging a positive benefit-cost ratio.7

      Furthermore, a conclusion of a study on wet-retroreflective pavement markings, Safety Evaluation of Wet-Reflective Pavement Markings (PDF, 111.01 KB) by the Federal Highway Administration report, Safety Evaluation of Wet-Reflective Pavement Markings found that “ … results suggest that the treatment—even with conservative assumptions on cost, service life, and the value of a statistical life—can be cost effective, especially for multilane roads.8

    • Reflective signage and pavement markings offer countries more affordable opportunities to reduce black spots on high-accident roads, help to reduce roadway crashes, and contribute to the progress being made by the United Nations, World Health Organization and country governments to stabilize and reduce road traffic fatalities around the world.

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