Pavement Deterioration

The World Bank's Deterioration of Unpaved Roads Model (DETOUR) implements in MS-Excel the road deterioration relationships for unpaved roads of the Highway Design and Maintenance Standards Model (HDM-III), which are the same as the forthcoming Highway Development and Management Model (HDM-4). DETOUR was developed for the World Bank Rural Transport Thematic Group and is designed primarily for engineered unpaved roads, of either gravel or earth surfacing, because the empirical models are based on a variety of such roads. When necessary it is possible to use the relationships also for tracks as a first estimate, but the user needs to be aware that the environmental effects of drainage and rainfall may be poorly represented. For more information regarding roughness and the economic aspects of low volume roads, visit the Design & Appraisal of Rural Transport Infrastructure Web page maintained by the World Bank Rural Transport Thematic Group.

This paper presents a proposal for modelling work zones in HDM-4. A worked example of the calculations is also given. It is an update of Bennett (1996) and Bennett (1998) with corrections to several equations and modifications to reflect the current version of the work zone effects software.

Report describing the development of the HDM-4 models

Realistic prediction of pavement performance is a critical component of asset management. Performance in terms of structural capacity is generally measured by the Adjusted Structural Number (SNP), hence a review has been carried out testing alternative methods for deriving this parameter for unbound granular pavements. Simplified methods may work reasonably well when calibrated to typical local conditions, but they are less likely to provide the same reliability in different regions or with different pavement structures. The rigorous methods (which can be readily applied) are recommended wherever deflection bowl information has been recorded. However, it is important to note that the standard equations are based on isotropic moduli for each layer, rather than anisotropic moduli, which the Austroads Pavement Design Guide has adopted for mechanistic analysis. Typical field measured moduli for unbound granular pavements are presented and appropriate calculation procedures suggested. Calibration or correction of SNP may also be required in a range of circumstances when refining the structural capacity for use in long-term pavement performance prediction. Where representative benchmark sites are set up and actual performance is monitored, appropriate calibration factors, based on specific modes of distress can be developed. These result in effective SNP values for a given network, giving due regard to the local range of materials and construction techniques.

Report on road deterioration and maintenance effects modelling.

Background to HDM-4 Rut Depth Modelling

Review of how the HDM-III RDME model was applied in different studies

This report is the original NDLI report describing the HDM-4 pavement deterioration and works effects models. Some of the models were refined, but it provides a lot of the background to the final HDM-4 models. It also includes models that were not included in HDM-4, such as for block pavements.