Retroreflective Sheetings Used for Sign Faces
Important Note: The current state of the retroreflective sheeting market is changing rapidly, 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. However, the information on this page may be slightly outdated as events develop.
There are a number of different types of retroreflective sheetings in use on highway signs.
Some types, as classified by ASTM D4956-01, are:
- Type I, also known as Engineer Grade:
Basic reflective sheeting, made up of very small glass beads enclosed in a translucent pigmented substrate. Has no distinctive identifying pattern, other than, of course, it reflects. This material is one of the most durable (in its ability to withstand rough handling) of all the sign sheeting products. Generally regarded to have a seven year service life. Produced by Avery-Dennison (T-1000 series), 3M (Scotchlite Engineer Grade 2200 and 3200), Nippon Carbide (Nikkalite Engineering Grade 7100 and 8100), and American Decal (Adcolite 180 and 280).
- Type II, also known as Super Engineer Grade:
Similar to Type I, except it uses larger glass beads, providing about twice the level of reflectivity of Type I sheeting. This sheeting can be identified by small trademarks which are screened into the sheeting (stars for Nikkalite, small As for Avery, etc.). Cost is less than twice that of Type I. Generally regarded to have a ten year service life. Produced by Nippon Carbide (Super Engineering Grade 17000 and 18000), Avery-Dennison (T-2000 series), and Kiwalite (Extra Engineer Grade).
- Type III, also known as High Intensity:
This sheeting is know as an "encapsulated lens" sheeting, made of 2 layers - an outer translucent pigmented layer, and an inner reflective layer faced with glass beads. The two layers are connected by a lattice, hence its distinctive 'honeycomb' appearance, where the lattice pattern varies by manufacturer for easy identification. This is currently the minimum recommended sheeting for ADOT regulatory, warning, and marker signs. Cost is about twice that of Type I. Generally regarded to have a ten year service life. Produced by 3M (Scotchlite High Intensity Grade 2870 and 3870), Avery Dennison (T-5000 series), Nippon Carbide (Ultra Lite Grade II), Kiwalite (22000), ATSM (High Intensity) and LG Chem (LG Lite).
- Type IV:
This is also a multi-layer sheeting, except that the reflective layer is made of microscopic cube-corner reflectors instead of glass beads - known as a "microprismatic" layer. This sheeting can be distinguished by the pattern of small "squares" superimposed upon a hexagonal lattice grid. This sheeting is about seven times as bright as Type I. Cost is comparable to type III. Generally regarded to have a ten year service life. Produced by 3M (Scotchlite High Intensity Prismatic Grade 3930), Avery Dennison (T-5900 and T-6000 series), and Nippon Carbide (Crystal Grade 92000 series).
- Type V:
This sheeting is made of a metallized microprismatic material. Used in delineators and raised pavement markers. Cost is about 5 1/2 times that of Type I. Generally regarded to have a five year service life. Produced by Reflexite (type AP-1000 and AR-1000).
- Type VI:
A vinyl backed microprismatic material. This sheeting differs from all other types by being composed of a flexible vinyl cloth, allowing it to be used for clothing and roll-up signs. Cost is about 6 times that of Type I. Generally regarded to have a two year service life. Produced by Reflexite (High Performance and Super Bright), 3M (RS20, RS30, 3840 series), and Avery Dennison (WU-6014).
- Type VII:
This is also a microprismatic sheeting. This can be distinguished by the diamond-shaped lattice separating the sheeting layers, and a "coarse" grain to the microprisms. This sheeting is about fourteen times brighter than Type I at shallow viewing angles. Cost is about 5 times that of Type I. Generally regarded to have a ten year service life. Produced by 3M (Diamond Grade LDP Series).
- Type VIII:
Also a microprismatic sheeting similar in design to Type VII and IX, but with distinguishing characteristics similar to Type IV. This sheeting is about six times brighter than Type I. Cost is about 5 times that of Type I. Generally regarded to have a ten year service life. Produced by Avery Dennison (T-7000 MVP series), Nippon Carbide (Crystal Grade 92000 series), and 3M (Diamond Grade NAP Series).
- Type IX:
A microprismatic sheeting very similar to Type VII, distinguished from Type VII by the "fine" grain of the microprisms. This sheeting is about six times brighter than Type I. Cost is about 5 times that of Type I. Generally regarded to have a ten year service life. Produced by 3M (Diamond Grade VIP Series) and Avery Dennison (T-9500 series).
- Type X:
A microprismatic sheeting very similar to Types VII-IX, and has similar performance characteristics. Generally regarded to have a ten year service life. Produced by Nippon Carbide (Crystal Grade 93000 series). Note that 3M 3930 High Intensity Prismatic and 3M Diamond Grade LDP also meet the performance criteria of Type X.
Sign sheeting manufacturers have developed newer sheeting types with improved performance, and ASTM is considering creating newer classifications to codify the performance characteristics of these newer sheetings. Example of this include 3M Diamond Grade DG3 and Avery Dennison Omniview.
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:
- Cut-out Letters and Symbols: directly applied to the sign face.
- Demountable Copy: This legend is made of reflective sheeting applied to thin aluminum, which is then cut out into the letter and legend shapes and then riveted to the sign face. This permits the sign legend to be changed or removed without having to replace the entire sign panel.
- Positive Silk-screen: Used for signs with legends darker than the background, such as most regulatory and warning signs. The legend is applied directly onto the colored sign face with opaque ink.
- Negative Silk-Screen: Used for signs with legends lighter than the background, such as STOP signs or Interstate shields. The process begins with a white sign face, then a translucent ink is applied onto the sign face, with the exception of the legend (or regions of other colors. This produces a white legend on a colored background.
- Overlay Film: Also used for signs with legends lighter than the background. The process begins with a white sign face, then the overlay film in the appropriate color is cut to remove the sections where the white is to show through. This overlay film is then applied onto the sign face.
Colored inks used in sign silk-screening are translucent to allow reflectivity through the ink, whereas black ink used for signs is opaque.
Inks are available from 3M, Nippon Carbide, Avery Dennison, Nazdar, and other manufacturers.
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, often fail structurally - the outer colored layer delaminates and falls off, exposing the silver reflective underlayer 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 Transportation Institute for their invaluable assistance in gathering this information.
More information may also be found from the Federal Highway Administration at
FHWA Retroreflective Sheeting Identification Guide
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Updated 15 September 2010 (coding)
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Retroreflective Sheeting Identification Guide provided courtesy of Federal Highway Administration.
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