Over the last 15 years, many road controlling authorities in New Zealand have had a policy to transfer more risk and responsibility into the private sector and to encourage clearer definition of the roles of client, engineer and contractor. Developing performance-based specifications is an obvious and appropriate mechanism for achieving this shared balance of risk. A deterioration model was developed, so that measurements of some critical criteria carried out after an initial proving period of the service life, can enable an assessment of future surface performance and hence, enable a system of proportional payment to the contractor based on value to the client. The performance-based concept was developed into a specification jointly by Transit New Zealand and the New Zealand Bitumen Contractors Association (now Roading New Zealand) and has been used successful in various sealing contracts for the last thirteen years. This paper describes the basis for the specification, the deterioration model developed to predict the loss of texture depth with time and traffic, and the philosophy behind some of the other acceptance criteria chosen. Experiences of both client and contractor in using this approach are incorporated into the discussion. (a) For the covering entry of this conference, please see ITRD abstract no. E217100.
Abstract