The potential impact of automotive headlight changes on the visibility of reflectorized highway signs.

All non-illuminated road signs require a relatively small quantity of upward headlamp illumination to be visible. Many European designs have sharply reduced this upward component, a design change which could also take place in the U.S. under current SAE standards. The paper develops lighting intensity values required for minimum overhead sign visibility, reviews the performance of current sealed-beam and European headlamps, and suggests some changes to SAE Standard J 579 c to assure the continued usefulness of these signs.