UK Roads Liaison Group

Defects Index Working Group

The Roads Board set up a Defects Index Working Group with representatives from the Road Performance Management Group (RPMG), the TTS / SCANNER Project Management Group (PMG) and the UKPMS Steering Group (UKPMS SG) to review the recommendations of the preliminary analysis carried out by the Chris Britton Consultancy, the proposed methodology, and determine thresholds and weightings.

From the preliminary analysis report, the Defects Index Working Group developed an initial definition for an overall defects index.  This identified which parameters should be included in the index, the initial settings for the thresholds and weightings and suggested some possible variations in the model.  The Group commissioned a further study to assess the suitability of the proposed threshold and weightings and compare the results with engineer’s assessments of road condition.

The Working Group made four main recommendations:

  • The ‘Defects Index’ should be named the ‘SCANNER Road Condition Indicator’
  • A new number should be allocated for the BVPI in England to demonstrate that there was no continuity between the new measure of road condition and previous measures (Deflectograph, Visual Inspection (CVI and DVI), and TTS)
  • The SCANNER RCI should be based on specific thresholds and weightings, and the parameters should be combined using specific relevance and reliability factors to give an overall score for each 10m subsection of carriageway
  • The indicator should be used to divide the network into three categories:
    • "RED" = lengths in poor overall condition which are likely to require planned maintenance soon (i.e. within a year or so) on a "worst first" basis. [Although there may be justification for postponing major repairs, and only carrying out minor repairs to keep the road safe and serviceable, in order to minimise whole life costs. i.e. "economic prioritisation"].
    • "AMBER" = lengths where some deterioration is apparent which should be investigated to determine the optimum time for planned maintenance treatment. [Where there may be justification for carrying out a lesser maintenance treatment sooner, rather than more extensive treatment later, in order to minimise whole life costs. i.e. "economic prioritisation"]
    • "GREEN" = lengths where the carriageway is generally in a good state of repair.

The recommendations were adopted by the Department for Transport for use in England and the thresholds and weightings, relevance and reliability factors for reporting 2005/06 surveys are given on the Department’s website are available here.