This paper reports on a three year study which was funded by the Science and Engineering Research Council (SERC) and was undertaken in collaboration with the Hertfordshire County Council and the Transport and Road Research Laboratory (now TRL). The objective of the project is to study the nature causes and rate of deterioration of minor roads and to identify warning levels for structural maintenance work to be effected on minor roads. A matrix approach wad adopted to categorise the physical characteristics of the sites to be investigated. It has been hypothesised that the causes of deterioration were road width (overriding), construction, drainage, edge support and traffic loading. From these factors a matrix with 20 cells was produced. A search was made for roads showing some degree of deterioration which would likely yield changes in condition over the study period and a few with no deterioration to act as a control. The study was confined to an area of approximately 600 km2 to the East, West and South of the Polytechnic at Hatfield, UK. Ultimately 74 sites, each comprising a 100 metre length, were identified. At each site, road cores were taken to determine the construction and composition. The underlying CBR was established using the Dynamic Cone Penetrometer. Observations were made at 6 month intervals using both manual visual inspection and mechanical surveys. The former consisted of the CHART survey augmented by DECHART in which a detailed mosaic was built up of conditions relating to the edge, rutting, cracking etc. The mechanical tests consisted of measurements by the High Speed Road Monitor (HRM) at 6 or 12 month intervals and the Deflectograph (2 sets of observations on half the sites) and finally the Falling Weight Deflectometer. The last mentioned was used to investigate the stiffness of the pavement in longitudinal and transverse directions in relation to changing condition. Deterioration rates were established for a number of conditions i.e. rutting and cracking for sites in each cell of the matrix. Detailed statistical analysis using regression and principal components techniques were used to establish the main causal factors of minor road deterioration. A second study of mainly urban sites was begun in 1990 with the aim of dividing economic models for highway maintenance strategies; this work is being undertaken jointly with four county councils, (Barnet, Buckinghamshire, Shropshire, and South Yorkshire (Sheffield)) in collaboration with WDM Ltd.
Abstract