There are several pertinent factors and considerations that have a direct bearing on the requirements contained in the attached Recommended Special Specification No. 50-R, and it seems appropriate to record them here as reference material either in support of the specification or as information.
Digital Object Identifier
Havens, James H., "Proposed Revision for Specification for Reflex-Reflective Materials for Highway Signs" (1954). Kentucky Transportation Center Research Report. 1264.