Modelling the long-term sustainability impacts of coordination policies for urban infrastructure rehabilitation.

Due to structural and hydraulic deterioration, urban water pipe networks have annual rehabilitation needs. Worldwide, these needs are often significantly larger than the actual amount of rehabilitation being performed, leading to increased risks of serious failures, lower performance and a growing techno-financial burden for future generations. It is well accepted that, in order to limit the multiple impacts of utility works in the urban environment, rehabilitation projects should be coordinated between water, transport, energy and telecommunication infrastructures. In practice, such coordination means that public utilities must rehabilitate assets earlier or later than technically needed, in order to engage in joint projects in which digging and resurfacing expenditures are shared. Hence, at the municipal scale, such coordination influences two variables that are key to strategic decision support: average costs (€/metre) for asset rehabilitation, and the service lifetimes of those assets. However, current models for strategic asset management do not enable practitioners to estimate how changes in the coordination process may influence the long-term financial and environmental impacts of infrastructure rehabilitation. The present study aimed at addressing this methodological gap by introducing the concept of a coordination window that quantifies to what extent utilities compromise asset rehabilitation times in order to join multi-utility projects. An algorithm for modelling the influence of the coordination window size on long-term sustainability costs is presented and applied to one Swedish municipality. The results suggested that total capital costs and carbon emissions can be lowered by 34% and 16% with a coordination window of 35 and 25 year, in comparison to the no-coordination case.