APPLICATIONS FOR 12-INCH SIGNAL INDICATIONS

DATA COLLECTED FROM A STUDY OF TRAFFIC SIGNAL OPTICAL UNITS ARE REVIEWED AND DISCUSSED. ABOUT SEVEN PERCENT OF THE LENSES OF SOME 3.2 MILLION SIGNAL OPTICAL UNITS WERE ESTIMATED TO BE OF TWELVE-INCH SIZE. PROJECTED FUTURE USAGE WOULD INVOLVE USE OF THIS SIZE LENS IN EIGHTEEN PERCENT OF ALL OPTICAL UNITS BY 1970. THE THEORY OF TWELVE-INCH LENS APPLICATION CONCERNS THE IMPORTANT INCREASE IN TARGET VALUE AT LOCATIONS WHERE A SMALLER SIGNAL INDICATION MIGHT TEND TO BE OVERLOOKED. SEVERAL SITUATIONS WHERE 12-INCH LENSES HAVE BEEN APPLIED ARE LISTED FROM THE 1961 MANUAL ON UNIFORM TRAFFIC CONTROL DEVICES: (1) RURAL INTERSECTIONS OR THOSE WITH HIGH APPROACH SPEEDS, (2) ISOLATED INTERSECTIONS OR THOSE WHERE SIGNALIZATION MIGHT BE UNEXPECTED, AS AT THE FIRST SIGNAL BEYOND A FREEWAY EXIT, (3) SPECIAL PROBLEM LOCATIONS SUCH AS THOSE WITH CONFLICTING OR COMPETING BACKGROUND LIGHTING, AND (4) INTERSECTIONS WHERE DRIVERS VIEW BOTH TRAFFIC CONTROL AND LANE DIRECTION CONTROL SIGNALS SIMULTANEOUSLY. LAMP WATTAGES ARE ALSO DISCUSSED. IT WAS FOUND THAT TWO-THIRDS OF THE TWELVE-INCH RED INDICATIONS HAVE 150 WATT LAMPS, BUT LESS THAN ONE-HALF OF THE YELLOW INDICATIONS ARE THUS EQUIPPED. IT IS FELT THAT THE USE OF LAMPS EXCEEDING THE 100 WATT SERIES FOR THE TWELVE-INCH YELLOW RESULTS IN TOO BRIGHT A DISPLAY AT NIGHTTIME. AS AN ALTERNATIVE, ELECTRICALLY-REDUCED WATTAGE CAN BE USED FOR THE YELLOW DURING NIGHT-TIME OPERATION. THIS HAS THE ADVANTAGE OF ALLOWING STANDARDIZATION OF LAMP SIZES FOR TWELVE-INCH LENSES, AND THEREFORE MAY SIMPLIFY MAINTENANCE. THE DIMMING CAN BE ACCOMPLISHED BY A TRANSFORMER OR RESISTOR.

• Supplemental Notes:
  • Vol 32, No 6, PP 18-21, 1 FIG, 4 PHOT
• Authors:
  • Box, P C
• Publication Date: 1967-11

Media Info

• Serial:
  • Public Safety Systems

Subject/Index Terms

• TRT Terms: Brightness; Data collection; Intersections; Lamps; Lane use control signals; Lenses (Optics); Night; Optical devices; Rural highways; Size; Traffic control devices; Traffic signals; Yellow
• Uncontrolled Terms: Traffic direction
• Old TRIS Terms: Isolation; Optical lenses; Optical unit
• Subject Areas: Highways; Operations and Traffic Management;

Filing Info

• Accession Number: 00225177
• Record Type: Publication
• Files: TRIS
• Created Date: Feb 13 1994 12:00AM