TRAFFIC CONTROL & ROADWAY ELEMENTS - THEIR RELATIONSHIP TO HIGHWAY SAFETY/REVISED. CHAPTER 6 SPEED AND SPEED CONTROL

THE RELATIONSHIP BETWEEN THE NUMBER AND SEVERITY OF ACCIDENTS AND VEHICLE SPEED HAS LONG BEEN THE SUBJECT OF DISCUSSION AND STUDY. DATA RELATING SPEED TO ACCIDENTS, ANALYSIS OF THE EFFECTS OF SPEED REGULATIONS ESPECIALLY IN REDUCING ACCIDENTS ARE REPORTED. THE STRUCTURING UNDER WHICH THE SPEED-ACCIDENT RELATIONSHIP IS PRESENTED IS: (1) SPEED CHARACTERISTICS AND SPEED SELECTION, (2) SPEED-SAFETY CONTROL AND SAFETY. THE EFFECTS OF SPEED ON SAFETY ARE REPORTED INCLUDING ACCIDENT TYPE, FREQUENCY, AND SEVERITY. A KEY LINK IN THE ACCIDENT-SPEED RELATIONSHIP IS THE NORMAL TRAVELING SPEED OF THE VEHICLE WHEN IT ENCOUNTERS THE ACCIDENT SITUATION AND THE IMPACT SPEED AT THE TIME WHEN THE MAJOR DAMAGE IS DONE. EXISTING EVIDENCE SUPPORTS THE THEORY THAT DRIVERS SELECT SPEEDS BASED ON THE CONDITION THEY ENCOUNTER ON THE ROAD AND NOT EXTERNAL CONTROLS OR THE SPEEDOMETER. STUDIES SHOW THAT THE SEVERITY OF ACCIDENTS IN TERMS OF DAMAGE, INJURIES AND DEATHS INCREASES EXPONENTIALLY WITH TRAVEL SPEED WHEN AN ACCIDENT OCCURS. ANGLE AND HEAD-ON COLLISIONS INCREASED LINEARLY AT A RELATIVELY SMALL RATE WITH INCREASING SPEED. ANGLE COLLISIONS CONSTITUTE 15 PER CENT OF THE TOTAL, BUT AT LOW SPEEDS WERE RESPONSIBLE FOR ONE-THIRD OF THE INVOLVEMENTS. THE HEAD-ON AND THE OPPOSITE DIRECTION COLLISION PROPORTION INCREASED WITH INCREASING SPEED, BUT WAS ALWAYS LESS THAN ONE-FIFTH OF THE TOTAL. IT IS KNOWN THAT THE MINIMUM ACCIDENT INVOLVEMENT RATE OCCURS FOR THOSE TRAVELLING AT AVERAGE SPEEDS RATHER THAN THOSE AT HIGH OR LOW SPEEDS AND THE SINGLE VEHICLE NON-COLLISION ACCIDENTS INCREASE EXPONENTIALLY WITH SPEED. SEVERAL STUDIES HAVE SHOWN THAT A CHANGE IN SPEED DISTRIBUTION FROM NON-NORMAL TO NORMAL, STATISTICALLY PRODUCES A SIGNIFICANT REDUCTION IN ACCIDENTS. BEFORE THE BENEFITS OF SPEED CONTROL CAN BE FULLY DETERMINED, THE EFFECTS OF LAW ENFORCEMENT ON SAFETY MUST BE UNDERSTOOD.

• 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:
  • Cleveland, D E
• Publication Date: 1970

Media Info

• Features: Figures; References; Tables;
• Pagination: 13 p.

Subject/Index Terms

• TRT Terms: Crash causes; Crash rates; Crash severity; Data analysis; Frontal crashes; Mathematical analysis; Motor vehicles; Side crashes; Single vehicle crashes; Speed; Speed control; Traffic crashes; Traffic law enforcement; Traffic safety
• Uncontrolled Terms: Speed differential
• Subject Areas: Highways; Operations and Traffic Management; Safety and Human Factors;

Filing Info

• Accession Number: 00220871
• Record Type: Publication
• Files: TRIS
• Created Date: Aug 3 1970 12:00AM