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Traffic Control Signs: How to Inspect for Minimum Retroreflectivity Levels

The 2009 edition of the Manual of Traffic Control Devices (MUTCD) mandates that all U.S. transportation agencies must implement a system to ensure minimum levels of sign retroreflectivity by January of 2012.  These new standards will ensure a higher degree of driver and passenger safety by ensuring that traffic control signs can be easily seen. 

While all agencies must comply with these directives, there are several methods for doing so from which they may choose.  These include various techniques for conducting nighttime inspections, such as the sign calibration, comparison panel, and consistent parameters procedures.  These are described in more detail below.

• In the calibration signs procedure, a field inspector compares road signage to a calibration sign that is stored between inspections, to make certain that its retroreflectivity does not degrade.  This is done from normal viewing distances from the inspector's vehicle.  Agencies must make certain that they have calibration versions of each color sign to use this method.

• The comparison panel procedure involves attaching a panel to a sign that has become minimally reflective.  This panel possesses retroreflective properties that match or exceed the lowest acceptable standards. The inspector visually inspects the sign/panel combination to determine whether the sign's retroreflectivity has deteriorated to an unacceptable level.

• In the consistent parameters inspection, a set of uniform guidelines is used to conduct the nighttime visual inspections.  At the heart of these guidelines is the principle that the factors initially used to create the minimum retroreflectivity standards are replicated for the subsequent inspections, with an eye towards roadside safety.  These factors include the use of a pick-up truck or SUV that is model year 2000 or newer, as well as the stipulation that the inspector be at least 60 years old.

An alternative way to measure retroreflectivity is to use a portable retroreflectometer to gauge the retroreflectivity of traffic control signs.  The normal method for doing this can be found here.  No matter which procedure is used, the benefits to driver safety and accident avoidance from ensuring adequate sign retroreflectivity are substantial.