A SECOND STUDY OF RELATIONSHIPS BETWEEN TIRE TREAD DEPTH AND THE LIKELIHOOD OF ACCIDENT INVOLVEMENT

A STUDY HAS BEEN PERFORMED TO DETERMINE THE RELATIONSHIPS BETWEEN AUTOMOBILE TIRE TREAD DEPTH AND THE LIKELIHOOD OF TRAFFIC ACCIDENT INVOLVEMENT. THE STUDY WAS UNDERTAKEN TO VALIDATE AND REFINE THE FINDINGS OF AN EARLIER EFFORT WHICH DEMONSTRATED AN INVERSE RELATIONSHIP BETWEEN TIRE TREAD DEPTH AND ACCIDENT INVOLVEMENT. THIS INVERSE RELATIONSHIP WAS USED TO DETERMINE THAT THE LEGAL MINIMUM TREAD DEPTH A MAJOR TASK OF THE STUDY WAS TO OBJECTIVELY DETERMINE THE RELATIVE CONTRIBUTIONS OF LOW TREAD DEPTH PER SE AND THE "NATURE" OF DRIVERS OPERATING WITH LOW TREAD DEPTHS TO THE ABNORMAL ACCIDENT EXPERIENCE AT LOWER TREAD DEPTHS. IN THE EARLIER WORK, THE POSSIBLEY CONTRIBUTING EFFECTS OF THE "NATURE" OF DRIVERS WHO OPERATE WITH LOW TREAD DEPTH TIRES WERE RECOGNIZED. THE RECOMMENDED 4/32 INCH LEGAL MINIMUM TREAD DEPTH WAS BASED UPON ASSIGNING ONLY 50 PERCENT OF THE PROJECTED ACCIDENT REDUCTION AS A BENEFIT. THE REMAINING 50 PERCENT WAS NOT EXPECTED TO MATERIALIZE BASED UPON THE UNCHANGED "NATURE" OF THE DRIVER. HOWEVER, THE FIFTY-FIFTY SPLIT WAS SUBJECTIVE AND WAS CHALLENGED AS SUCH. TIRE TREAD DEPTH MEASUREMENTS WERE COLLECTED FOR A SAMPLE OF VEHICLES INVOLVED IN TRAFFIC ACCIDENTS AT THE TIME OF MOVING TRAFFIC VIOLATION. A SECOND SAMPLE WAS ACQUIRED FROM VEHICLES INVOLVED IN MOVING TRAFFIC VIOLATIONS WHERE THERE WAS NO ACCIDENT. USING THE PROPENSITY FOR MOVING TRAFFIC VIOLATION AS AN INDICATOR OF DRIVER "NATURE", RELATIVE INVOLVEMENTS FOR BOTH SAMPLES WERE COMPUTED BY COMPARISON WITH THE DISTRIBUTION OF TIRE TREAD DEPTHS FOUND IN THE POPULATION AT LARGE. THIS ANALYSIS PRODUCED A MORE OBJECTIVE DETERMINATION OF THE PROPORTION OF ABNORMAL ACCIDENT OCCURRENCE AT LOWER TREAD DEPTHS THAT COULD BE ASSIGNED THE LOWER TREAD DEPTH PER SE. AGAIN, THIS PROPORTION WAS FOUND INVERSELY RELATED TO TIRE TREAD DEPTH. USING THESE DISCOVERED PROPORTIONS, AN ANALYSIS WAS PERFORMED TO DETERMINE THE LEGAL MINIMUM TIRE TREAD DEPTH BELOW WHICH MOTORISTS WERE APT TO INCUR MORE COSTS IN ABNORMAL ACCIDENT INVOLVEMENT THAN COULD BE SAVED BY POSTPONING THE PURCHASE OF NEW TIRES. AGAIN, THE DESIRED LEGAL MINIMUM TREAD DEPTH WAS FOUND TO BE 4/32 INCH. IT IS RECOMMENDED THAT THE STATES ENACT LEGAL MINIMUM TREAD DEPTHS OF 4/32 INCH. ALSO, THAT THE FEDERALLY REQUIRED TIRE "WEAR INDICATOR", NOW CONSTRUCTED IN THE TIRE AT 2/32 INCH REMAINING TREAD DEPTH, BE MOVED TO THE 4/32 INCH DIMENSION. THE LARGE NUMBER OF TIRES FOUND TO BE ILLEGAL ACCORDING TO PRESENT STANDARDS DEMONSTRATES THE NEED FOR MORE EFFECTIVE ENFORECEMENT EFFORTS. /AUTHOR/

• Corporate Authors:

  Highway Safety Foundation

  Mansfield, OH  United States 
• Publication Date: 1972-5

Media Info

• Features: Figures; References; Tables;
• Pagination: 37 p.

Subject/Index Terms

• TRT Terms: Legal factors; Tire treads; Tires; Traffic crashes
• Uncontrolled Terms: Motor vehicle accidents
• Subject Areas: Highways; Law; Safety and Human Factors; Vehicles and Equipment;

Filing Info

• Accession Number: 00224203
• Record Type: Publication
• Source Agency: Nat Safety Council Safety Res Info Serv
• Files: TRIS
• Created Date: Jul 17 1973 12:00AM