BEFORE AND AFTER ACCIDENT STUDIES. SIGNIFICANT ACCIDENT REDUCTION. LOOK-UP TABLES FOR POLICE OFFICERS, TRAFFIC ENGINEERS AND ROAD SAFETY OFFICERS. FOR NON-STATISTICIANS

The tables show the number of accidents, "a", at the site in the after period, required for a statistically significant change (5% level) for a given number of accidents, "b", at the site in the before period shown on the top line of each page of the tables, and for a given control ratio, "C", shown down the extreme left hand column. Two values of "A" are given for each control ratio, the top value is the number of accidents in the after period required for A significant increase and the lower value of "a", is that required for a significant decrease in accidents. The report describes how to set up a before and after study. /TRRL/

  • Corporate Authors:

    Hertfordshire County Council

    Highway Department, Goldings
    Hertford, Hertfordshire,   England 
  • Publication Date: 1976-1

Media Info

  • Features: Tables;
  • Pagination: n.p.

Subject/Index Terms

Filing Info

  • Accession Number: 00179962
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Report/Paper Numbers: Report No. HCC 240-1Monograph
  • Files: ITRD, TRIS
  • Created Date: Sep 27 1978 12:00AM