RoadVista Retroreflectometers for Road Signs and Sign Sheeting
922 Handheld Retroreflectometer: Ensures a cost effective, safe, absolute means of meeting the minimum retroreflectivity requirements for traffic signs. Captures measurements for any type of retroreflective material and measures to ensure compliance with MUTCD minimum retroreflectivity requirements.
932 Handheld Retroreflectometer: Patented design to fully characterize the retroreflection (RA) and retroreflected night-time (CIE1931xy) color of road signs, high visibility safety clothing and other materials.
933 Retroreflectivity Workstation: Benchtop four-axis goniometer system for testing sign sheeting and high visibility clothing. Inspecion Q&A test tool for quick testing at multiple measurement geometries.
940D Photometric Range System: Ultimate platform for photometric testing of retroreflective materials. Provides complete and accurate retroreflection measurements.
1000 Retroreflection Monitoring System: Measurement system specially designed for retroreflective sheeting material production line monitoring.
In January 2008, the second revision of the MUTCD was released. It introduces language establishing minimum retroreflectivity levels that must be maintained for traffic signs. By January 2012, all agencies must implement a sign assessment and management program. The RoadVista Model 922 is an integral component of any program to maintain minimum retroreflectivity levels.
Measurement Standards for Road Signs
The standard used for signs is the Coefficient of Retroreflection (RA). A description of this can be found in ASTM Standard E808-91. It is defined as the coefficient of luminous intensity, RI , of
a plane retroreflecting surface to its area. The metric unit for RI is candelas per lux per square meter (cd/lx/m²).
The coefficient of luminous intensity is the ratio of the luminous intensity of the retroreflector in the direction of observation, Eˆ, to the illuminance at the retroreflector on a plane perpendicular to the direction of the incident light. After taking into account all of the units and other considerations, RA is conceptually identical to the coefficient of retroreflected luminance but simpler to implement for signs. One must note that the English units for RA (candelas per foot-candle per square foot) are often used. It is also often referred to as Specific Intensity per unit Area (SIA) in older documents and specifications; use of this term should be discouraged.
RA is still a ratio of returned intensity to incident illumination divided by the area of the retroreflector. Signs make the measurement of these quantities simpler because they have a fixed area. In addition, the measured geometry is arranged so that the plane of the sign is perpendicular to car headlights, thus the area does not change as fast as angles near horizontal. This makes the measurement much simpler and more accurate.