This report presents the results of an assessment of the SCANNER Road Condition Indicator (RCI) carried out by TRL.
The investigations have included a comparison between RCI results and engineer’s opinions at the site level, and investigation at the network level using a data set covering over 9000km of the local road network. These assessments have shown that the methodology employed in the SCANNER RCI to assess pavement condition is generally sound, but also identified a need to modify a number of the thresholds and weightings used.
As a result of this work, a revised set of weightings and thresholds have been proposed. These revisions to the RCI result in the maximum possible score for any subsection reducing from 370 to 315 on A or B roads, from 370 to 290 for rural C or U class roads, and from 370 to 270 on urban C or U class roads.
The effect of the new thresholds and weighting on the RCI values reported on the network sample has been demonstrated.
Thresholds and weightings have been proposed for the new measures of transverse unevenness (ADFD) and edge condition. A method for calculating an ‘Extended RCI’ is proposed, including assessments of transverse unevenness, and edge condition.
Work has been carried out to assess the sensitivity and confidence of the RCI results to the proportion of the network surveyed, in order to derive recommendations for the proportion of the network to survey. From this work, minimum survey lengths are recommended for networks of different lengths, to obtain 95% confidence that the reported percentage Red lies within ±0.75 of the true value.
A simple trajectory tool has been developed to assist local authorities in exploring the possible consequences of different maintenance scenarios on the condition of their network. This applies simple assumptions to a dataset representing the initial condition of a network, and explores how the network condition evolves over a period of 5 years.

Want to know more about this project?