Assessment of pavement impacts of development: lessons from the Department of Transport and Main Roads by Bradley Jones

Abstract

The Department of Transport and Main Roads (TMR) recognises that an increase in the number or size of vehicles using a road can significantly increase the costs associated with maintaining road pavements. Over 20 years, TMR guidelines for pavement impact assessments have evolved considerably. In the absence of their own guidelines, many local governments specify that developers should assess the pavement impact of proposed developments in accordance with TMR guidelines. However, local governments frequently do not appreciate the obligation this specification places on them to provide the data required for the assessment. Experience with TMR gives developers an expectation that pavement impact assessment should be simple while still realistic and accurate. This places an onus on local governments to maintain the relevant datasets and conduct the data processing required for developers to complete the assessment. The two (2) greatest challenges in preparing pavement impact assessments are estimating remaining pavement life and maintenance costs. The earliest TMR guidelines attempted to estimate remaining pavement life from pavement design life data, however, the data was generally unavailable. To address this missing information, TMR have used deterioration models to estimate remaining pavement life from current conditions. The first attempt to do this was an overly simplistic deterioration model based on current surface roughness, but this has evolved into sophisticated models based on current pavement strength. Local governments need to review the asset data that they currently have and determine how it can be converted to remaining pavement life for the purpose of pavement impact assessments. Estimates of maintenance costs based on first principles appear to have a greater validity than estimates based on historical data. If a first principles estimate of maintenance costs is used, it should have a dependence on traffic load that is consistent with the methodology for calculating developer contributions