Failure of critical services

Failure of critical services is a threat stemming from the failure of infrastructures to provide (the required quality of) services that are critical for the performance of a function. In this definition, services include the provision of products.

The threat by this definition concerns disturbances in organisations that are out of the span of control of the urban planner. These problems have causes that can be traced back to one of the other threat types, but as we have no influence on the causes of the disturbances, they are in effect irrelevant to the problem, which is that the required services are not or not sufficiently delivered.

This means that the only types of measures against this type of threat are either:


 * Reduction of the dependency on the service; or
 * Increase of the reliability / resilience of the service.

The threat of failure of critical infrastructure is particularly of interest to urban objects that are themselves part of the critical infrastructure, such as movable bridges, telecommunication towers or sewage plants.

Societal aspects
It is generally acknowledged that failure of built critical infrastructure, such as malfunctions and accidents in transportation, health service, emergency care or power supply, has an impact on the social components of a system. If an infrastructure-endangering event occurs, domino effects and/or cascading effects are very likely due to interference or outages of the critical infrastructure. Those effects have the potential to bring different sectors of society to standstill. In addition to direct harm to citizens and economic losses, this can generate also loss of confidence in the political system. Complexity of social consequences from critical infrastructure failure increases with increasing citizens’ dependence on the respective infrastructure, including critical services. Furthermore, crisis behaviour also depends on the predominant social patterns and legal frameworks, on the general legitimacy of political, economic and social institutions and on the amount of risk tolerance of the population.

Dependency theory
Critical infrastructure can be dependent on other CI in many ways. A power failure, for instance, can affect the telecommunication infrastructure and cause a decreased call handling capacity of the mobile phone system. This service disturbance may cause other CI, which use the communication services in its critical processes, to experience disruption. For example, a drinking water production organisation uses telecommunication links to remotely monitor its processes at the wells. After failing, the organisation must send employees to the remote sites to monitor the process and manually change settings, open valves, etc.. Power failure can also affect the transportation system: traffic lights cease to function, bridges that will not open or close, etc.; all resulting in severe traffic problems. These traffic problems can in their turn hamper the travel of the employees to the remote sites.

The above example illustrates the risk of cascading effects and thus underlines the importance of understanding these dependencies. The couplings between infrastructures are called dependencies when there is a uni-directional relationship between two infrastructures through which the state of the depending infrastructure is influenced by or is correlated to the state of the other. A coupling between the infrastructures is called an interdependency when two infrastructures are directly or indirectly (via another infrastructure) mutually dependent on each other.



Figure 1 depicts the dependency of the drinking water infrastructure on the telecommunications sector. Most of the drinking water treatment and especially the distribution systems are remotely monitored and controlled by the use of SCADA-systems. The use of public telecommunication networks - such as leased lines, mobile telephony, and internet - as the transportation network for SCADA-data collection and control information makes the drinking water infrastructure directly dependent of the telecom infrastructure and its services. A disturbance in the telecommunication system potentially may have cascading effects on the drinking water infrastructure.



Figure 2 depicts an interdependency between the electric power grid and the natural gas network. Natural gas may fuel generators that produce electricity. On the other hand, elements of the natural gas infrastructure - such as gas conditioning plants, compressors and computerised controls - may require electrical power to operate. A disturbance in the electrical grid may result in the loss of natural gas pressure which in turn can curtail the generation of electrical power.