A PRELIMINARY EXAMINATION OF THE OPTICAL PERFORMANCE OF ROAD TRAFFIC SIGNAL LIGHTS

SEVERAL INVESTIGATIONS AND REPORTS SUGGEST THAT A RED ROAD ROAD TRAFFIC SIGNAL LIGHT SHOULD HAVE AN ON-AXIS INTENSITY OF AT LEAST 200 CANDELAS. OTHER REPORTS SHOW THAT SIGNALS CURRENTLY USED HAVE INTENSITIES BELOW THIS VALUE. THIS PAPER REPORTS AN INVESTIGATION TO DETERMINE WHETHER THE 200 CANDELAS INTENSITY REQUIREMENT COULD BE MET WITHOUT RADICAL CHANGE OF THE TRADITIONAL OPTICAL DESIGN OF SIGNALS. BY JUDICIOUS CHOICE OF REFLECTOR, LAMPS AND REFRACTOR, AND BY CAREFUL FOCUSING IT IS SHOWN THAT AN ON-AXIS INTENSITY OF OVER 400 CANDELAS CAN BE ACHIEVED WHILST STILL RETAINING AN ADEQUATE DISTRIBUTION OF LIGHT. /AUTHOR/