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IRQB Insights: Critical Path

IRQB Insights is an article series introducing various technical aspects of rail quality and the IRIS Certification scheme. The article series helps to explain and provide insight to the operational matters of the certification and quality management processes.

The critical path methodology assessed during the IRIS Certification process is a basic requirement for the project time management set in the ISO/TS 22163 Clause

Critical path is defined in ISO 21500 as a “sequence of activities that determine the earliest possible completion date for the project or phase”.

Critical path should therefore be understood as a sequence of activities that are timely or logically linked to one another. Every single planned activity must be finished on time to avoid any project delays. Therefore, the critical path is also defining the minimum duration of a project.

These project activities can, for example, be:

  • type tests with a defined period of testing time such as fatigue test for wheelset axles, 1.000h salt spray tests;
  • delivery times for e.g., castings and forgings;
  • CE or TSI approval to fulfil contractual requirements.

Milestone planning and the critical path planning are different from each other as the critical path does not contain any time provisions in each of its elements.

For IRIS Certification, the maturity level for the requirements can be improved by using:

  • an application software for scheduling;
  • implementation of an early warning system to react on issues on the critical path and;
  • identification and mitigation of risks in the critical path.



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