Note on DRC Input Values

Overview This note provides guidance regarding input values for the carriageway DRC calculation. The input values must be entered by the user when running the UKPMS report, and are as follows:

 TINI: The time (years, 0dp) to when deterioration is first measurable by the survey being conducted.

 TTUL: The time (years, 0dp) to when the pavement is unserviceable and needs replacement.

 Renewal Unit Rate: The average surfacing renewal rate (£/m2, 2dp)

 Average width: The average carriageway width (m, 1dp)

TINI and TTUL The values recommended by HAMFIG for SCANNER data are given in Table 1.

Survey Type Road classification TINI TTUL A roads 7-8 21 SCANNER Other roads 4-6 21 Table 1: Range for SCANNER data

Research carried out for HAMFIG indicates that these values give an average national depreciation of around 50%. Note also that SCANNER picks up early signs of deterioration that do not have an impact on depreciation so using a value of zero for TINI (as indicated in the previous version of this guidance) may not be appropriate. In view of this authorities should make an engineering judgement about the onset of initial deterioration and not rely wholly on SCANNER outputs. See clause 8.5.3.2 of the Code of Practice on Transport Infrastructure Assets (CIPFA, 2010)

For CVI and DVI data, HAMFIG does not recommend any change to the previous guidance so the recommended range of values remains as given in Table 2.

Survey Type Road classification TINI TTUL CVI or DVI All roads 5-9 17-25 Table 2: Range for CVI or DVI data

Renewal Unit Rate No values are supplied for the renewal unit rate. This must be established by each local authority based on their local rates. Guidance is provided elsewhere to indicate what to consider when setting up the unit rates.

Average Width If required UKPMS can calculate the average carriageway width based on the local authority’s inventory data. If UKPMS inventory data is not available, the local authority must supply a value for the average carriageway width. The average carriageway width must be derived from evidence; from 2011/12 the use of default values for carriageway widths is not permitted.