Photometer for measurement of reflex-reflective sign materials. Paper for presentation at the Annual Meeting of the Highway Research Board (HRB), January 1968.

A proposed photometer was evolved after careful review of the geometrics of the typical highway environment encountered by the motorist. A comparison of photometric readings taken with the proposed prototype meter and the classic darkroom tunnel method at 0.2 and 0.5. divergence angle is shown. Colour samples representing the colour spectrum employed on highway signs were tested. Further, a comparison with a rigorous visual nighttime series of observations was made.