ASTM D-4956 - 11 Retro Reflective Sheeting Types and 5 Adhesive Classes

ASTM D-4956 Regulations identify 11 types of retro-reflective sheeting for signs. It also lists 5 classes or types of adhesive backings. Retro-reflectivity, observation angles, photo-metrics, durability, and color characteristics determine the type, 1 - 11.  Minimum standards must be met for each type. In general, the higher the tape type, the brighter the tape, but this is not always so.  Type 5 sheeting would be an example of this. Adhesive backing classes are classified by the application of the sheeting.  Where it will be installed and how.

Retro Reflective Sheeting Types (ASTM D-4956) - Candela ratings based on a .2 observation angle/-4 entrance angle.

• Type 1 - Engineering Grade  (Glass Bead Based Sheeting - Enclosed Lens) Rated at 75 Candelas for White - actual.  Available in standard and flexible versions.
• Type 2 - Super Engineer Grade (High Index Glass Bead Based - Enclosed Lens) Rated at 140 Candelas for White - actual. 

• Type 3 - High Intensity (High Intensity Glass Bead Film - Encapsulated Lens) Rated at 250 Candelas for White - actual.  Available in standard and flexible versions.
• Type 4 - High Intensity Micro Prismatic Rated at 360 Candelas for White - minimum.  Air backed prismatic film.  Acrylic construction.
• Type 5 - Super High Intensity Sheeting for Delineators. Typically a thin metalized film - rugged and incredibly bright.  Rated at 700 Candelas for White - up to 2000 Candelas for .1/-4 observation - actual. Polyester based film. Not an air backed film.
• Type 6 - Elastomeric flexible retroreflective sheeting with no adhesive on the back - Roll up Sign Material.  Rated at 160 Candelas for Pink - minimum. Air backed film.  Vinyl or PVC based for flexibility.
• Type 7 - Discontinued and Replaced by Type 8 Sheeting.

• Type 8 - Retro Reflective sheeting typically manufactured as an unmetalized cube corner Micro-Prismatic retroreflective element material. Rated at 700 Candelas for White - actual.  Acrylic based film.  Air backed prismatic. 
• Type 9 - Wide Observation Angle Reflective Film.  Normally manufactured as an unmetalized cube corner material with micro-prismatic elements. Rated at 380 Candelas for White - minimum.  Acrylic based film.  Air backed prismatic. Viewable at wider angles.  Used for ground mounted signs.
• Type 10 - Discontinued and Replaced by Type 8 Sheeting. 
• Type 11—All Observation Angle Retroreflective Sheeting.  Normally manufactured using Non Metalized cube corner Micro-Prismatic retro-reflective elements. Rated at 580 Candelas for White - minimum.  Used for overhead signs on interstates and highways.

Adhesive backing classes -

• Class 1 - Pressure-sensitive adhesive No heat or solvent required for application. Peel backing and press on. Most common backing.

• Class 2 - Adhesive activated through the use of pressure and heat.
• Class 3 - Repositionable pressure-sensitive adhesive with a low tack. 
• Class 4 - Low-temperature (-7°C) pressure sensitive adhesive for colder climate applications.
• Class 5 - Non-adhesive backing.  Used for roll up signs.  Temporary traffic signs.