Porterbrook Leasing Company and South Western Railway has collaborated with Fishbone to investigate maintenance optimisation on legacy fleets. Significant operational and financial benefits were achieved on the Class 455 fleet, through extension of the level 1 to 4 maintenance periodicities.


Client: Porterbrook Leasing Limited

Location: UK

Services: Engineering

Maintenance optimisation enables Rolling stock leasing Company’s (ROSCOs) and Train Operating Company’s (TOCs) to realise significant availability and cost improvements to their fleets while ensuring that fleet reliability is maintained.

Fishbone Solutions delivered a 5,000 mile Level 1 to 4 exam extension by:

  • Reviewing component maintenance and condition at exams
  • Establishing a safe, monitored mileage extension trial
  • Reassessing component condition at extended mileages and presenting a case for extension based on expert condition assessment and mitigations, particularly through changes to level 1 to 4 maintenance tasks
  • Level 1 to 4 maintenance tasks were reviewed for suitability to run to extended mileages themselves based on unit maintenance histories and failure modes
  • A controlled programme of trial running was conducted to ascertain any requirements for change to wear limits, component inspections, and task periodicity
  • Proposal for changes to C4 periodicity was presented to the TOC / ROSCO supporting the changes and other interventions required to optimise the overall benefit
  • The fleet was certified to run extend mileages for both regimes
  • Level 1 to 4 maintenance periodicity was increased from 15,000 to 20,000 miles enabling the Operator to retain fleet availability levels post timetable change


Fishbone has successfully completed similar level 1 to 4 exam extensions on two other fleets for Porterbrook and SWR. We are currently undertaking a maintenance optimisation review for Porterbrook, with the aim of optimising C6 overhaul either as wholesale maintenance regime change or extended reduced scope C6 periodicity.

How can we help?

Luke Essex

Head of Project Engineering View Profile

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