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THE IMPACT OF RISK ON WHOLE OF LIFE COSTING

This paper presents a methodology that allows risk assessment to be utilized in the whole-of-life costing analysis of pavement alternatives. To assist in the optimization of pavement design and selection, it supplements and enhances previous independent work carried out for the Australian Asphalt Pavement Association (AAPA). The impact of risk on whole of life costing is addressed through a procedure proposed to assist in maximizing the reliability of the final selection. Risk is the issue that provides a revised view and procedures proposed for comparison of alternatives. In the proposed method, a number of feasible alternative pavement designs are determined in the usual manner for comparison using the whole-of-life cost approach. A risk assessment of each alternative is then carried out to take into account not only the initial cost of construction of each alternative, but also all the maintenance and rehabilitation costs that may occur during the life of the pavement, and an estimate of the salvage value of the pavement at the end of its design life, if this is considered applicable. Under certain circumstances road user costs are not taken into account in this analysis, this needs careful consideration as their exclusion needs to be justified. As an example, for heavily trafficked roads and other high usage roads such as through shopping centers, the cost of traffic disruption resulting during pavement maintenance and rehabilitation works may be high with considerable associated social implications. Care also needs to be taken with heavily trafficked roads to ensure that maintenance operations minimize traffic disruption. This can be achieved by ensuring that, wherever possible, structural rehabilitation can be carried out in an automated fashion on surface layers only. The risks associated with each whole-of-life pavement scenario need careful consideration. In the proposed procedure, risks are allowed for by the application of a "design reliability factor", which is similar to a multiplier for the calculated design traffic. Following a similar approach to the draft revised Austroads pavement design system, this broad based approach has attempted to take into account a number of uncertainties which includes, but is not limited to: (1) uncertainty in estimating design traffic loading; (2) variations in in-situ materials properties as constructed and over the life of the pavement; (3) variations in pavement layer thicknesses; and (4) accuracy of the design method for various pavement types. This procedure presents a rational assessment of risk, project reliability and the likely whole-of-life cost estimation. The impacts of uncertainties are more easily quantifiable and, to a certain extent, controllable for the particular project analyzed.

Language

  • English

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Filing Info

  • Accession Number: 00964441
  • Record Type: Publication
  • ISBN: 087659229X
  • Files: TRIS, ATRI
  • Created Date: Oct 24 2003 12:00AM