Certain requirements must be met for a tape to be certified as DOT C2, C3, or C4. These rules cover how the tape is made, what color it is, how wide it is, how far apart the different colors are, performance, and how reflective it is. The manufacturer can put DOT C2 certification on a tape only if it has been tested and found to meet these standards. Here are the details of the certification requirements. (Federal Motor Carrier Safety Administration 393.11 is the source.)
Construction – The requirements for the basic construction of the film are very straight forward. This is how virtually all reflective tapes are constructed. The regulations are as follows:
S5.7.1.1 Construction. Retroreflective sheeting shall consist of a smooth, flat, transparent exterior film with retroreflective elements embedded or suspended beneath the film so as to form a non-exposed retroreflective optical system.
Color – DOT tape shall be constructed with white and red alternating colors. (Note – the white color on prismatic tapes often looks silver but reflects white at night.) The phrasing of the FMCSA regulation is as follows:
(a) Retro-reflective sheeting shall be applied in a pattern of alternating white and red color segments to the sides and rear of each trailer, and to the rear of each truck tractor, and in white to the upper rear corners of each trailer and truck tractor, in the locations specified in S5.7.1.4, and Figures 30–1 through 30–4, or Figure 31, as appropriate. (see this article for placement details)
Spacing -The red and white (silver) sections of the tape are required to be a minimum of 12 inches plus or minus 6 inches. That would be between 6″ and 18″ There is an exception provided when the tape must be trimmed to avoid obstructions when installed. In addition, neither the red or white colors can exceed two thirds (2/3) of the total. This is the reason behind the 7/11 and 6/6 patterns.
There are two types of DOT tape available. A 7″ white / 11″ red and a 6″ white / 6″ red. If you run the numbers you will see that both meet the spacing requirement. On 7/11 tape the 7″ white would represent 39% of the aggregate and the 11″ red would represent 61%, so neither would exceed 2/3 or 66%. The 6/6 would be 50% each. To the best of my knowledge all 50 states allow you to use either the 7/11 or 6/6 type DOT tape. The specific regulation is listed below:
(b) Except for a segment that is trimmed to clear obstructions, or lengthened to provide red sheeting near red lamps, each white or red segment shall have a length of 300 mm ±150 mm.
(c) Neither white nor red sheeting shall represent more than two thirds of the aggregate of any continuous strip marking the width of a trailer, or any continuous or broken strip marking its length.
Width – DOT certified tape can be 2″ wide, 3″ wide or 4″ wide. The most popular and cost efficient size is 2 inches but for larger trucks many users prefer the 3 and 4 inch widths in either the 6/6 or 7/11. 2″ wide tapes are C2, 3″ are C3, and 4″ are C4. The general principle is that the more visible the truck the better, and in the event of an accident it is important to be able to show due diligence when it comes to making the truck as visible as possible. The specifics of the FMCSA regulation is as follows:
(d) Retroreflective sheeting shall have a width of not less than 50 mm (Grade DOT-C2), 75 mm (Grade DOT-C3), or 100 mm (Grade DOT-C4).
Reflectivity & Performance – This is one of the most important characteristics of DOT tape. A bright tape is easier to see from further away. This is very important for highway applications. To meet the DOT C2,3,4 requirements, a tape must meet all the ASTM D4956-90 Type V Sheeting requirements EXCEPT the requirement for reflectivity. These requirements would include things like adhesion, colorfastness, pliability, shrinkage, weathering, etc… The requirements for reflectivity are much the same as for Type III or High Intensity Glass Bead tape or greater. A Prismatic DOT tape is recommended for safety. This will make sure that the reflectivity goes way beyond what is needed. Here are the exact words of the regulation and a chart showing minimum reflectivity:
S5.7.1.2 Performance requirements. Retroreflective sheeting shall meet the requirements of ASTM D 4956–90, Standard Specification for Retroreflective Sheeting for Traffic Control, for Type V Sheeting, except for the photometric requirements, and shall meet the minimum photometric performance requirements specified in Figure 29.
(e) The coefficients for retroreflection of each segment of red or white sheeting shall be not less than the minimum values specified in Figure 29 of this standard for grades DOT-C2, DOT-C3, and DOT-C4.
Figure 29—Minimum Photometric Performance of Retroflective Sheeting in Candela/Lux/Square Meter
| ENTRANCE ANGLE | OBSERVATION ANGLE | GRADE | |||
|---|---|---|---|---|---|
| 0.2 DEGREE | 0.5 DEGREE | ||||
| WHITE | RED | WHITE | RED | ||
| -4 degree | 250 | 60 | 65 | 15 | DOT–C2 |
| 30 degree | 250 | 60 | 65 | 15 | DOT–C2 |
| 45 degree | 60 | 15 | 15 | 4 | DOT–C2 |
| -4 degree | 165 | 40 | 43 | 10 | DOT–C3 |
| 30 degree | 165 | 40 | 43 | 10 | DOT–C3 |
| 45 degree | 40 | 10 | 10 | 3 | DOT–C3 |
| -4 degree | 125 | 30 | 33 | 8 | DOT–C4 |
| 30 degree | 125 | 30 | 33 | 8 | DOT–C4 |
| 45 degree | 30 | 8 | 8 | 2 | DOT–C4 |
DOT Certification Logo: At least every 12 inches, the tape should say “DOT-C2.” The characters should be at least 3 mm tall and stamped with indelible ink or an equivalent. Here are the exact words:
S5.7.1.5 Certification. The letters DOT-C2, DOT-C3, or DOT-C4, as appropriate, constituting a certification that the retroreflective sheeting conforms to the requirements of S5.7.1.2, shall appear at least once on the exposed surface of each white or red segment of retroreflective sheeting, and at least once every 300 mm on retroreflective sheeting that is white only. The characters shall be not less than 3 mm high, and shall be permanently stamped, etched, molded, or printed in indelible ink.
Steven Cole (Economics, MBA – University of West Florida , Business & Innovation – Stanford University) 25 years of experience in the reflective safety business. Specializing in vehicle accident and rear end collision reduction through increased visibility.