The decision-making process to select the investment strategy should align with the approach to asset management and, in particular, provide the most efficient and affordable way of achieving the performance requirements. Typically, the selection of maintenance strategies considers the following:
A number of techniques may be used to select the investment strategy, some of which are listed below. The International Infrastructure Maintenance Manual (IIMM, 2015) also gives advice on these decision-making techniques.
Risk-based evaluation focuses on minimizing the risk associated with the asset through an investment strategy while ensuring that any risks are managed at the minimum cost. The approach to risk management is described in section 2.3. Risk evaluation can be used as a decision-making technique on its own or considered with the other decision support techniques described below.
Whole-life cost is a cost-benefit analysis that quantifies the investment costs, including the cost of the treatment and subsequent maintenance interventions, against economic benefits, including safety, traffic delays, and pollution. These should be assessed for each maintenance strategy. The maintenance strategy with the lowest NPV over the period of analysis provides the lowest whole-life cost. Costs may be determined as described above. Benefits should be determined by each organization and considered in the context of its overall approach to asset management.
Multi-criteria analysis may be used to prioritize competing treatment options from which the maintenance strategy may be selected. A number of criteria may be selected that align with the levels of service and/or goals and objectives of the organization. Typically, these may include safety, serviceability, sustainability, and accessibility. A weighting to demonstrate the relative importance of these factors may be selected from which an overall score is determined. The necessity to meet statutory requirements needs to be reflected in the scoring. This technique can be used where benefits and costs are less tangible to define. However, it supports a qualitative assessment as well as a quantitative one.