This document is focused on the resilience of transport systems to specified events. It can be used by any organization that is interested in measuring resilience regardless of size or extent of infrastructure. As transport can occur on infrastructure of multiple types, the measures of service and resilience are also suitable for infrastructure enabling multi-modal transport.
Considering the context of potentially disruptive events, this document is to be used to determine:
— how to measure the service provided by, and the resilience of, transport infrastructure;
— how to set service and resilience targets of transport infrastructure.
This document includes:
— the concepts of how service and resilience can be measured;
— the concepts of how service and resilience targets can be set;
— the steps to determine how to measure service and resilience;
— the steps to set service and resilience targets.
Even if the probability of occurrence of the event is required in the estimation of the system resilience to
a specific event, this document provides no guidance as to how to estimate the probability of occurrence
of these events. In such situations, this document is to be used to measure the resilience to discrete events whose probabilities of occurrence change over time. Along the same lines, this document is not a complete guideline as to how to conduct a risk assessment of a transport system, of which the resilience
to specified events is a part. Instead, it can be used to assess the resilience with respect to the events that are defined in the risk assessment.
This document points out that the assessment of resilience requires, either explicitly or implicitly the modelling of the transport system in space and time, which include the consideration of the interconnections between infrastructure components or between events, including cascading events. It does not, however, provide guidance as how to specifically model these, as the modelling required depends greatly on the specific situation being investigated.
This document also points out that it is essential to define the service being provided by a transport system as a precursor to the assessment of resilience. It does not, however, impose requirements on the services to be considered nor the levels of precision required, as the services considered and the precision
required depend greatly on the specific situation being investigated. For the same reasons, this document does not provide specific information on the organisational requirements to assess resilience, e.g. in terms of human resources, financial skills, partners, schedules or data sources. These requirements depend greatly on purpose of the resilience assessment and the amount of effort the organisation would like to invest, the detail of the resilience estimates they would like to have, and the type of the infrastructure and events to be investigated.
Finally, although the use of expert opinion is recommended in this document in numerous places, no specific guidance is given to which of the plethora of tools and methods that exist should be used. The tools and methods that should be used must be determined on a case-by-case basis and special care is required to ensure their independence.