TRAFFIC SIGNAL VISIBILITY

IN MOST INSTANCES OF "MADE-TO-ORDER" LAYOUTS OF INTERSECTION SIGNALIZATIONS, THE ACCIDENT EXPERIENCE HAS BEEN LOWER THAN THAT AT INTERSECTIONS WHOSE LAYOUTS FOLLOWED THE USUAL PATTERNS. THE MOST ESSENTIAL CHARACTERISTIC OF THE DESIGN APPEARED TO BE THE VISIBILITY OF THE INDICATIONS TO DRIVERS. ADEQUATE VISIBILITY IS ACHIEVED BY CAREFUL PLACING OF SIGNALS. AS THE DISTANCE BETWEEN THE OBSTRUCTING VEHICLES AND THE STOP-LINE SHORTENS, THERE IS A CORRESPONDING SHORTENING OF THE DISTANCE BETWEEN THE OBSTRUCTING VEHICLES AND THE STOP-LINE SHORTENS, THERE IS A CORRESPONDING SHORTENING OF THE DISTANCE OF THE SIGNAL VISIBILITY, AS MEASURED BY THE DRIVER OF THE OBSERVING VEHICLE, TO THE OBSERVING VEHICLE. THERE CLEARLY IS A NEED FOR INSTALLING IN ALL CASES AT LEAST ONE SIGNAL TO THE LEFT OF THE DRIVER. IN SOME INSTANCES IT WAS FOUND ADVISABLE TO PLACE A FOURTH SIGNAL AS A FAR-RIGHT POST-HEIGHT INDICATION. AT LEAST TWO INDICATINS ARE REQUIRED FOR EVERY APPROACH TO A SIGNALIZED INTERSECTIONS, TO SUPPLY BOTH MOTORISTS AND PEDESTRIANS WITH PROPER GUIDANCE, AS WELL AS TO PROVIDE FOR BACK-UP SIGNALS IN CASE OF AN OUTAGE. INDICATIONS SHOULD BE SPACED BETWEEN 20 AND 30 FEET LATERALLY. PROPER VISIBILITY FOR PEDESTRIANS SHOULD NEVER BE FORGOTTEN IN THE COURSE OF THE LAYOUT. SPECIAL VISORS OR BACK-PLATES MAY BE USED TO ADVANTAGE IN SOME INSTANCES. /AUTHOR/

• Supplemental Notes:
  • 16 Pp, 3 FiG, 6 TAB, 3 REF
• Corporate Authors:

  Institute of Traffic Engineers

  2029 K Street, NW
  Washington, DC    20006
• Publication Date: 1970-7

Media Info

• Serial:
  • Institute of Traffic Engineers Technical Reports
  • Publisher: Institute of Traffic Engineers

Subject/Index Terms

• TRT Terms: Location; Traffic signals; Visibility
• Old TRIS Terms: Placement
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00225949
• Record Type: Publication
• Files: TRIS
• Created Date: Apr 25 1971 12:00AM