AASHTO M 268-15 pdf free download
AASHTO M 268-15 pdf free download.Retroreflective Sheeting for Flat and Vertical Traffic Control Applications.
3.3.1. For sheeting not meeting the 20 percent maximum rotational sensitivity requirement, the manufacturer must provide identification marks or other features (such as a datum mark, tiles, or distinct seal pattern) in or on the sheeting face denoting the optimum orientation of the sheeting. The markings or features must be visible from a minimum distance of 2 ft and must be arrayed in such a manner that they will be readily distinguishable on cutout legends, symbols, or borders. The manufacturer must provide fabrication guidelines outlining optimum sheeting orientation upon user request.
3.3.2. When utilizing sheeting that does not meet the 20 percent maximum rotational requirement, fabricate signs by applying white sheeting for cutout legends, symbols, borders, and route marker attachments within the parent sign face in the optimum rotation according to the identification markings; and apply all background sheeting uniformly oriented.
3.4. Delineators—Rctroreflective sheeting materials suitable for use on delineators are typically of microprismatic construction. The Type of retroreflective sheeting shall be specified by the user.
4. CLASSIFICATIONS
4.1. This specification establishes four types of retroreflective sheeting, with successively increasing minimum coefficients of retroreflection. Retroreflective sheeting materials shall meet all of the performance requirements in Section 5 to qualify as a particular type under this specification. Minimum coefficients of retroreflection are shown in Tables 4, 5, 6, and 7 for retroreflective sheeting Types A, B, C, and D, respectively. The designated type is exclusive to the highest specified minimum R4 satisfied at observation angle of 0.5 degrees and an entrance angle of 4.0 degrees. Using higher retrordflectivity sheeting to manufacture signs where lower retroretlectivity sheeting Types are specified must be approved by the end user.
4.2. The following are general descriptions of the types of retroreflective sheeting established by this specification. These are provided for descriptive information only and are not intended to be limitations or recommendations.
Note I -—The Manual on Uni/brni Trafile control Dc’’ices (MUTCD) requires that traffic control signs, unless illuminated, be retrorefiective to show the same shape and similar color both day and night. Therefore, any retroreflective sheeting materials meeting this specification would satisfy that requirement. However, when determining the appropriateness of a particular type of sheeting for a particular application, consideration should be given to the pertinent highway characteristics where the materials will be installed, such as traffic volumes, traffic speeds, and roadway geometrics, as well as available resources. Brighter materials (meeting Type B, C, or D) should be considered for use on complex roadway environments where the driving task may be more involved.
4.2.1. Ti.pe A—Retrorefiective sheeting materials meeting Type A are typically constructed of encapsulated microscopic glass bead lens construction.
4.2.2. Type B—Retroreflective sheeting materials meeting Type B are typically constructed of unmetallized microprismatic optics. These triangular microprismatic materials do not have a significant 1-degree observation angle performance.
4.2.3. T3pe (‘—Retroreflective sheeting materials meeting Type C are typically constructed of unmetallized microprismatic optics. These triangular microprismatic materials have a significant I -degree observation angle performance.
4.2.4. Type D—Retroreflective sheeting materials meeting Type D are typically constructed of unmetallized microprismatic optics. These materials have 0.5- and 1-degree observation angle performance approximately two times greater than Type C materials.AASHTO M 268-15 pdf download.
