Ethical discounting for civil infrastructure decisions extending over multiple generations

Life-cycle performance, safety, reliability and risk are emergent issues for civil infrastructure systems exposed to recurring natural and man-made disasters. In recent years, there has been a growing awareness of the importance of socio-economic sustainability in research and practice in the field of civil infrastructure. Sustainable engineering solutions strive to achieve responsible stewardship of available resources and to avoid transferring the burden of costly maintenance or repair of civil infrastructure to future generations. The use of customary risk-informed decision frameworks, however, raises ethical issues in terms of project risk shared between current and future generations, especially when project expectations require it to function over extended periods of time that may be a century or more. In this paper, the relation between intergenerational equity in decision support frameworks for civil infrastructure is explored. We propose an intergenerational discounting method for civil infrastructure to achieve equitable risk sharing between current and future generations, and investigate the impact of discounting in life-cycle engineering on future generations and on sustainable decision-making. The effect of the proposed discounting method on decision consequences is highlighted through two examples; seismic retrofit of a dam and seismic design of a steel frame building.