This is the first of several papers dealing with the development and description of the signal glass specification formulated by the Signal Section of the Association of American Railroads in 1935 and 1938. The present paper gives the spectral transmissions of the basis standards—red, yellow, green, blue, purple and lunar white glasses—on which the A. A. R. scale of luminous transmission is based, and defines that scale in fundamental, absolute units. Comparison is made with the scales defined in the 1908 and 1918 signal glass specifications.
KASSON S. GIBSON and GERALDINE WALKER HAUPT, "Standardization of the Luminous Transmission Scale Used in the Specification of Railroad Signal Glasses," J. Opt. Soc. Am. 29, 188-200 (1939)