Risk-based lifecycle analysis for road structures: the benefit of an improved risk-based funding allocation method for maintenance and rehabilitation of road structures under budget constraints

Abstract

With the current environment of slow economic growth in South Africa as well as the negative economic impact of the COVID-19 epidemic placing additional constraints on the national fiscus, resources made available for the management of the nation’s economic infrastructure are even more scarce, stressing the need for asset managers to optimally apply the limited available funding across asset portfolios. While methods for allocating limited funding to competing infrastructure across a network of assets are highly developed for road pavements, current funding allocation methods defined in the TMH 22 for road structures are primarily based on direct assessments of condition and urgency from the field assessor and do not incorporate lifecycle performance, lifecycle cost, or any economic parameters in the prioritisation of expenditure on assets. An alternative funding allocation method using a risk-based lifecycle analysis (RBLA) focused on achieving the optimal balance in asset performance, cost, and risk (driven by economic, environmental, and social factors) has been implemented by one of the largest metropolitan municipalities in South Africa. This paper compares the projected impact of the two different funding allocation methods on the long-term performance of road structure asset portfolios using the municipality’s condition assessment data for general bridges. The comparison is made to investigate and quantify the benefits arising from adopting the RBLA method under resource constraints instead of the conventional TMH 22 method. The RBLA resulted in insignificant changes in overall condition over a five-year assessment cycle but a notable reduction of risk of 24% when compared to the investment alternatives identified by the current TMH 22 method of prioritising structures. This indicates that under constrained funding levels, a higher return in terms of risk reduction benefits is possible for the same expenditure when implementing RBLA selected investment alternatives. It is, therefore, recommended that this method be considered by industry practitioners and further investigated and considered by COTO for improvement to current industry practices.