Manual of Traffic Signs

Retroreflective Sheetings Used for Sign Faces

Important Note: The current state of the retroreflective sheeting market is continuing to change, due to development of new sheetings, requested changes to ASTM D4956, and changes in product offerings by manufacturers. This webpage will try to keep up with current events in reflective sheetings as they develop.

There are a number of different types of retroreflective sheetings in use on highway signs.
Some types, as classified by ASTM D4956, are:

Important Note: The Types used in the ASTM sheeting specifications do not necessarily imply relative performance; i.e. a "higher"-type sheeting isn't necessarily better than a "lower"-type sheeting - it just meets different performance characteristics. Also note that some sheetings can meet the criteria of several ASTM Types.

Nearly all sheetings are available with pressure-sensitive backings for attachment to sign surfaces. Some sheetings are available with heat-activated backings, but with changes in sign manufacturing technology this type of adhesive is becoming less popular and less available.

Sign legends for retroreflective signs are produced by the following methods:

Colored inks used in sign silk-screening are translucent to allow reflectivity through the ink, whereas black ink used for signs is opaque.

Sheeting types normally fail in different ways, depending on how they are structured.

Single-layer types, such as Type I or II, usually fail by gradually losing their retroreflective intensity. This is due to increasing opacity of the pigmented material caused by ultraviolet ray exposure due to sunlight.

Multi-layer sheetings, such as Type III through Type XI, often fail structurally - the outer colored layer delaminates and falls off, exposing the underlying reflective layer to the elements, and ruining the contrast needed for legibility.

If properly applied and sealed to a good surface, most reflective sheetings are quite water, ice, and salt resistant.

Special thanks to Seth Chalmers of Chalmers Engineering Company and H. Gene Hawkins Jr. of Texas A&M University for their invaluable assistance in gathering this information.

More information may also be found at the Federal Highway Administration's webpages on sign retroreflectivity.

FHWA Retroreflective Sheeting Identification Guide

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Updated 09 December 2015

Scripting: Richard C. Moeur
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Retroreflective Sheeting Identification Guide provided courtesy of Federal Highway Administration.
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