Rapid inspection methods have been developed to measure and classify: 1) the key physical characteristics (surface condition and roughness, width available, slope, curvature, residual utility of previous investment in drainage, foundation and surface (if any); 2) its natural environment (terrain, rainfall patterns, soils, availability of materials, environmentally sensitive areas) and 3); its social environment (land use patterns, user characteristics). These methods can be sophisticated and relatively expensive, using GPS, electronic measuring devices and video to produce a continuous image of road characteristics from a moving vehicle. They will usually provide data for estimating both costs and potential benefits. Certain simulation models, such as HDM-4, RED and RONETS will perform the cost calculations for each category. They are not usually viable for low-volume road inspection as the precision they provide is sometimes superfluous and always costly. When roads are simple and resources to apply complicated analyses are not available locally it is better to simply use recent bids or actual costs incurred in similar works.
Simple methods exist using simple standardised forms or laptops on which summary data on road conditions can be coded at 100-200m intervals, relying on visual inspection of road conditions and some simple measurements. These provide a rapid and cheap basis for approximate cost estimation providing sample lengths are not too short and the volume of data collected is modest. The design of procedures and forms requires clear knowledge of how the data collected will be processed. Without it the results will be incoherent and irrelevant.
It must be emphasized that surveys, whether automated or manual, are expensive in terms of logistics and subject to differing opinions. Therefore.when many inspectors are involved it requires training and close supervision to ensure that data collected is consistent and complete.
Each short section of road is surveyed thus and located within a matrix of upgrading alternatives, and consolidated over a reasonably homogeneous length of road for costing purposes. The data collected will be sufficient to assign each length to a unique category of road to which a cost index can be assigned, which takes account of its physical and environmental characteristics.