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THE PART VISIBILITY COULD PLAY IN ROAD DESIGN

A PHYSIOLOGICAL DESCRIPTION OF SEEING IS PRESENTED, INCLUDING BLINKING, LIGHT AND DARK ADAPTATION, AND THE METHODS OF MEASURING VISION. WORK HAS BEEN DONE ON THE DYNAMIC TESTING OF VISUAL ACUITY IN WHICH THE TEST OBJECT IS MOVED AND THE SUBJECT VIEWS IT IN MOTION. IT IS HELD THAT ANY DYNAMIC TESTING OR FILM SCREENING OF A ROAD SCENE, TO CHECK ACUITY OR DRIVING HABITS, SHOULD REQUIRE THE OBSERVER TO BE IN MOTION, NOT NECESSARILY THE OBJECT. IF THE OBSERVER IS IN MOTION THERE IS THE ACCOMPANYING CONFUSION IN PERIPHERAL VISION, OWING TO THE WHOLE OF THE VIEW MOVING AND CAUSING CEREBRAL CONFUSION; BOTH OF THESE CONDITIONS DISTINQUISH VISION USED IN DRIVING FROM ORDINARY VISION. CAUSES OF DIMINUTION IN THE EFFICIENCY OF THE EYE INCLUDED DISEASES PECULIAR TO THE EYE OR FROM GENERAL BODILY DESEASE, AND SEDATIVES WHICH REDUCE THE INTENSITY OF REFLEX ACTION. AS PERIPHERAL VISION IS OF MAJOR IMPORTANCE IN DRIVING, MORE EXPERIMENTS SHOULD BE UNDERTAKEN IN THIS AREA. THE EFFECT OF OTHER TOXIC AGENTS IS ESTIMATED. PERCEPTION IS DISCUSSED AS COMPOSED OF THE FOLLOWING COMPONENTS: FORM, DISTANCE, AND SIZE. THE EFFECT OF DISTRACTIONS AND OF MOVEMENT IS EVALUATED. IT IS UNDERSCORED THAT WHEN A DRIVER IS IN MOTION HIS ABILITY TO PERCEIVE DIFFERS FROM THAT OF THE STATIONARY HUMAN BEING. AS SPEED INCREASES SO DO THE NUMBER OF SITUATIONS WHICH REQUIRE A DECISION, ESPECIALLY THE PERCEPTION OF AN OBJECT OUTSIDE THE DIRECT PATH OF TRAVEL. ROAD DESIGN STANDARDS INVOLVING SIGHT DISTANCE APPEAR TO HAVE ACCEPTED THAT A HUMAN BEING HAS A HIGH STANDARD OF VISUAL ACUITY WITHOUT TAKING INTO ACCOUNT THAT MAY OCCUR. THIS IS ILLUSTRATED IN THE FACT THAT THE HEIGHT OF AN OBJECT FOR ROAD DESIGN PURPOSES SEEN OVER A CREST SHOULD BE ZERO; SEEN AROUND A HORIZONTAL CURVE IT MAY BE 9 INCHES BY DAY AND ON SHARP CURVES ZERO BY NIGHT. AN OBJECT THAT CAN BE SEEN BY DAY OVER A CREST OR AROUND A HORIZONTAL CURVE MAY NOT NECESSARILY BE SEEN AT THE SAME DISTANCE AT NIGHT OWING TO THE HEADLIGHTS OF THE VEHICLES POINTING DIRECTLY AHEAD. ROAD DESIGN PROBLEMS ARE CONSIDERED IN RELATION TO OVERTAKING, HORIZONTAL VERSUS VERTICAL SIGHT DISTANCE, SIDE VISION, OVERHEAD AND FOREGROUND VISION, AND THE DESIGN OF INTERSECTIONS. THE DRIVER AND THE VEHICLE ARE DISCUSSED IN GENERAL TERMS WITH REGARD TO ANTICIPATION OF A HAZARD, REACTION TIME IN URBAN CONDITIONS, GUIDE MARKS, AND FLASHING LIGHTS ON THE VEHICLE. THERE IS A NEED TO EQUIP CARS WITH LIGHTS WHOSE MESSAGE TO OTHER DRIV- ERS IS EMPHATIC, CLEAR, UNIFORM AND VIVID. IT IS CONCLUDED THAT MANY MOVEMENTS MADE BY A DRIVER IN HANDLING A VEHICLE ARE CONDITIONED REFLEXES; THE DRIVER WHO RELIES MORE ON THOUGHT AND LESS ON CONDITIONED REFLEX IS A BETTER DRIVER. /AUTHOR/

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  • Accession Number: 00223194
  • Record Type: Publication
  • Source Agency: Nat Safety Council Safety Res Info Serv
  • Files: TRIS, ATRI
  • Created Date: Sep 9 1970 12:00AM