Road infrastructure asset management requires making decisions that affect how infrastructure provides service – for example, the intervention strategies to follow for specific assets, the intervention programmes to implement for entire networks and the way for interventions to be executed once it is decided that they should be executed. These decisions should be made to maximise the net benefit of infrastructure for all stakeholders and be made consistently and transparently. Currently, the definitions of service used by road infrastructure asset managers either are incomplete or are built on combinations of metrics, which give an idea of service but do not measure service directly. Neither allows for consistent and transparent decision-making that leads to the maximisation of the net benefit for all stakeholders. In this paper, a definition of the service provided by road infrastructure is provided that enables consistent and transparent decisions to maximise the net benefit for all road infrastructure stakeholders. The service definition is used to determine the net-benefit-maximising intervention strategy that shows its usefulness and its ability to let stakeholders see how they will be affected by decisions and that all of their concerns have been adequately taken into consideration when decisions are made.

The difficulties of engineers and managers agreeing on how to invest in infrastructure maintenance stem from a basic inability to communicate with each other. This leads to the suboptimal management of infrastructure. Luckily, this situation can be remedied by engineers learning how to communicate their concerns in a way that managers can understand, so that they can clearly see whether a proposed action needs to be taken or can be deferred. This paper shows, with the help of a realistic example, in terms of infrastructure, methodology and techniques, how this can be done. The proposed approach, although upon reading is perhaps intuitive, is starkly absent in the literature in the field of infrastructure asset management. In the proposed approach, it is demonstrated how to improve the traditional approaches used by engineers to communicate to managers through (a) the quantification of the level of service as seen by mangers, (b) the modelling of how infrastructure might not provide the required level of service and (c) the way of showing how intervention programmes can affect the provision of service, both now and in the future.

Because failures on railway lines have nonzero probabilities of occurrence and can result in significant costs if they occur, railway infrastructure managers are interested in determining intervention programs that best reduce this risk, taking into consideration their budget constraints. In this paper, a base model is proposed to determine optimal risk-reducing intervention programs for railway lines based on the states of its objects and budget availability. The base model is an integer nonlinear model with an objective function that maximizes net benefit without exceeding budget constraints. The net benefit is the difference between the amount of risk reduction and the costs of executing interventions in terms of both direct costs (i.e., materials and labor forces) and indirect costs (i.e., the travel time costs). Three variations of the base model, i.e., the object model, the block model, and the line model, are used to investigate the trade-offs between increasingly simplified models and decreasing ability to determine the optimal intervention program due to decreasing ability to accurately estimate costs and benefits. In the object model, objects are considered in isolation, i.e., while each object fails and is restored all other objects in the line are fully functional. In the block model, blocks are observed in isolation, i.e., while each block fails and is restored all objects in the line are fully functional, whereas the multiple objects within a block may fail and be restored simultaneously. In the line model, all objects in the line may fail and be restored simultaneously. Fault tree analysis is used in the block and line models to estimate the costs of the combined failures of multiple objects. The three models are demonstrated by using them to determine the optimal intervention program for a fictive railway line between two stations that consisted of eight track sections, a bridge, two switches, and two signals. The intervention programs determined using the three models in terms of the interventions included and the net benefit obtained are compared. It is shown that all three variations produce useful results but that there are significant differences in the estimation of the net benefits using the three different models, and that these differences lead to different interventions being included in the determined intervention programs, and consequently in the net benefit that will be achieved through their implementation. It was also shown that each improvement in the estimation of accuracy comes with an increase in modeling complexity.