1. Home
  2. TRID
  3. View Record
https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

TRAFFIC CONTROL & ROADWAY ELEMENTS - THEIR RELATIONSHIP TO HIGHWAY SAFETY/REVISED. CHAPTER 4 INTERSECTIONS

STATISTICS SHOW THAT INTERSECTIONAL ACCIDENTS ARE A NATIONAL PROBLEM IN HIGHWAY SAFETY. ABOUT 24 PER CENT OF FATAL ACCIDENTS LISTED IN A NATIONAL TABULATION WERE CLASSIFIED AS OCCURRING AT INTERSECTIONS. IN URBAN AREAS, APPROXIMATELY 41 PERCENT OF TOTAL ACCIDENTS, AND 39 PER CENT OF FATAL ACCIDENTS, WERE REPORTED AS INTERSECTIONAL. IN RURAL AREAS, THE DATA SHOWED THAT 27 PER CENT OF TOTAL ACCIDENTS, BUT ONLY 17 PER CENT OF FATAL ACCIDENTS, WERE AT INTERSECTIONS. INTERSECTION ELEMENTS WHICH CAN BE RELATED TO INTERSECTION ACCIDENT RATES INCLUDE GEOMETRIC LAYOUT AND TRAFFIC CONTROLS. THE BASIC INTERSECTION CONFIGURATIONS INCLUDE THE L, Y, T, OFFSET (JOG), AND CROSS-TYPE. IN A COMPARISON OF UNCONTROLLED INTERSECTIONS IN LIMITED-ACCESS SUBDIVISIONS, THE CROSS-TYPE WAS FOUND TO HAVE 14 TIMES THE ACCIDENT FREQUENCY AS THE T-TYPE. ACCIDENT FREQUENCY FOR CROSS-TYPE INTERSECTIONS IN GRIDIRON SUBDIVISIONS WAS 41 TIMES THAT OF T-TYPE. THE INTERSECTION SHAPE WAS ALSO FOUND TO BE AN IMPORTANT ELEMENT AT RURAL LOCATIONS. CROSS-TYPE INTERSECTIONS OF INDIANA COUNTY ROADS WERE FOUND TO EXPERIENCE AN ACCIDENT FREQUENCY FOUR TIMES THAT OF T AND Y- TYPES. ACCIDENTS WERE STUDIED AT LOW-VOLUME RURAL INTERSECTIONS ALONG MINNESOTA HIGHWAYS. TRAFFIC VOLUME WAS FOUND TO HAVE THE GREATEST EFFECT ON ACCIDENT FREQUENCY AT CROSS-TYPE INTERSECTIONS. THESE STUDIES POINT QUITE STRONGLY TO THE DESIRABILITY OF USING T-TYPE INTERSECTIONS FOR LOCAL STREETS IN BOTH URBAN AND RURAL AREAS. AN IMPORTANT DESIGN ELEMENT INVOLVES PROVISION FOR VEHICLES TO MAKE LEFT TURNS OFF MAJOR ROUTES. LEFT-TURN CHANNELIZATION WAS INSTALLED AT 40 UNSIGNALIZED URBAN AND RURAL INTERSECTIONS ALONG CALIFORNIA HIGHWAYS AND ACCIDENTS WERE FOUND TO BE REDUCED SIGNIFICANTLY. THE TYPES OF INTERSECTIONAL CONTROLS INCLUDED IN THE DISCUSSION ARE YIELD, TWO-WAY STOP, FOUR-WAY STOP, AND THE TRAFFIC SIGNAL. THE YIELD SIGN IS USED TO REGULATE TRAFFIC FLOW AT LOW VOLUME INTERSECTIONS AND AT INTERSECTIONS WHERE THE ACCIDENT RATE IS ABOVE THE AVERAGE OF OTHER INTERSECTIONS OF THE SAME TYPE. YIELD SIGNS WERE FOUND TO BE AN EFFECTIVE MEASURE AT PREVIOUSLY UNCONTROLLED, ISOLATED, URBAN, LOW- VOLUME INTERSECTIONS IN BERKELEY, CALIFORNIA, WHERE ACCIDENTS WERE REDUCED 44 PER CENT AT A TOTAL OF 13 INTERSECTIONS, AND IN SEATTLE, WASHINGTON, WHERE A 52 PER CENT REDUCTION AT A TOTAL OF 30 INTERSECTIONS WAS ACHIEVED. THE FINDINGS OF VARIOUS RESEARCHERS INDICATE THAT YIELD SIGNS CAN BE AN EFFECTIVE CONTROL UNDER MANY LOW VOLUME CONDITIONS. SEVERAL STUDIES ARE REPORTED ON TWO-WAY STOP CONTROL. THE STUDIES INDICATE FOR TWO-WAY STOPS THAT: (1) ACCIDENT RATES INCREASED AT CROSS-STREET VOLUME INCREASED, AND (2) ACCIDENT RATE DECREASED AS MAIN STREET VOLUME INCREASED. FOR FOUR-WAY STOPS, ST. PAUL AND CALIFORNIA STUDIES SUPPORT A CONCLUSION THAT ACCIDENT REDUCTION CAN BE EFFECTIVE IF THE INSTALLATION IS WARRANTED BY ACCIDENT FREQUENCY AND THE VOLUMES ARE MODERATE AND BALANCED. MANY STUDIES ARE REPORTED ON THE EFFECT OF TRAFFIC SIGNALS ON TRAFFIC OPERATIONS. STUDIES ON FLASHING BEACONS AND DIRECTIONAL SIGNING ARE DESCRIBED.

  • Supplemental Notes:
    • The Automotive Safety Foundation published the first three chapters in this series. The remaining nine chapters were published by the Highway Users Federation for Safety and Mobility.
  • Corporate Authors:

    Highway Users Federation for Safety and Mobility

    1776 Massachusetts Avenue, NW
    Washington, DC  United States  20036
  • Authors:
    • Box, P C
  • Publication Date: 1970

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 12 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00220872
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 27 1970 12:00AM