A model track record

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As is the case with every railway, track is fundamental to the safety and performance of London Underground, requiring a high-value and complex asset management and investment plan to be delivered over several decades. To achieve this, effective whole-life cost modelling tools are becoming increasingly essential to explore the implications and benefits of different asset management scenarios.

In January 2003, Metronet Rail was awarded a 30-year contract for the maintenance, renewal and upgrade of approximately two-thirds of London Underground’s network under a Public-Private Partnership (PPP). But the company got into financial difficulties in 2007 and was taken in-house by London Underground.

The arrangement effectively required the company to move from an annual budget-driven, often patch-and-mend, approach to an engineering planning process focussed on achieving target levels of performance and infrastructure condition, with asset management plans specifying maintenance and renewal works over a moving nine-year timeframe.

In 2006 Metronet developed what became known as the Track Condition Model (TCM) in order to support production of “economic and efficient” workbanks. The model included all rails, ballast, concrete base and sleepers for the Metronet-managed lines and rigorous engineering validation was used to forecast work plans out to 2017/18 and report against PPP benchmarks.

The Track Condition Model

Built in Microsoft Excel, the TCM proved a success, becoming a core tool for track asset management and independently recognised as very good practice within the industry. It was continuously developed over time to take account of improved asset knowledge and, as its use increased, it quickly led to demands for expansion in both scope and functionality. However, whilst Excel is a versatile software package, it ultimately proved to be a significant constraint, unable to keep pace with ever improving asset management capabilities and aspirations. Scenario modelling was becoming increasingly important but was complicated and time-consuming using the TCM; it also wasn’t auditable, with results difficult to evaluate side by side.

There was a long-standing ambition to model the ‘whole asset’ – including track drainage, conductor rails, P&C etc – within the same system and to have a decision support tool that could accommodate this. Further, there was an ever-increasing need for the logic and rationale of investment plans to be highly transparent in order to allow decisions to be defended and, where necessary, challenged and improved. The modelling logic contained within the TCM was buried in algorithms, many of which were over 200 characters long and not always understood.

As summed up by Peter Belcher, Track & Track Drainage Renewals Sponsor, “In a very few years’ time we will have a suite of ever-growing line-based models that will be very difficult – perhaps impossible – to manage, process, analyse and report the data from. And from a position of being best practice, it will fall to the opposite.”

Requirements and solution

In 2009 Metronet decided to replace the TCM with an off-the-shelf decision support tool, preferably one that would not require significant change to existing asset management processes. Other key requirements included –

• Usability: ensuring that asset managers readily understand how the software operates and how different modelling relationships and assumptions drive workbanks and forecasts.

• Integrity: any modelling errors or areas of weak data must be readily identifiable and straightforward to resolve.

• Informed: both in terms of inputs – such as the easy import of data from existing sources – and outputs – the ability of asset managers to review, validate and, where necessary, amend automatically generated workbanks.

• Transparency: asset managers must be able to easily communicate the rationale behind their preferred asset management plan.

• Powerful: it must have the ability to include all lines in one model and evaluate any number of user-defined planning scenarios.

• Future proof: the tool must be easy to develop in parallel with improving asset knowledge.

Advanced software tools

SEAMS’ WiLCO® was selected as the preferred successor to the TCM, as it most clearly demonstrated that it had the flexibility to quickly replicate the data and modelling relationships contained within the previous models whilst delivering immediate benefits in terms of integrity, efficiency and functionality.

WiLCO – an acronym for Whole Life Cost Optimisation – is a purpose-built off-the-shelf suite of advanced software tools that support asset managers in ensuring that their plans are based on transparent and informed decisions made in a high integrity environment. Originally developed to aid utility companies in optimising the value of their investment into physical infrastructure assets, WiLCO provides a powerful yet flexible and user-friendly toolset for developing models that forecast asset condition, residual life, required interventions, outturn performance, cost and risk.

As LUL had a number of specific requirements relating to its asset planning processes – such as the need for WiLCO to allow hands-on engineering validation of asset renewal workbanks through a visual ‘grid’ – the LUL track renewal team, Chrome Angel Solutions and SEAMS worked together to rapidly configure the standard software suite in parallel with actual model development.

The WiLCO track model went live in early 2010 after a 12-week implementation project. The resulting model includes all rails, sleepers and ballast on the operational network for those lines previously managed by Metronet (Metronet Rail having been ‘reabsorbed’ by London Underground Ltd immediately prior to the implementation project). The model is used to forecast future asset condition – influenced in part by volume of traffic – and to recommend annual asset renewal activities up to 30 years ahead in order to achieve asset condition and performance targets within given funding constraints.

Having met the original requirement of replicating the TCM in a more stable and powerful platform, LUL is now looking to extend the functionality of the model. The next step is to incorporate track maintenance activities, cost and performance metrics which are currently modelled in Excel using the residual life output from the TCM to forecast the impact of asset renewals on maintenance.

Article courtesy of the rail engineer magazine.

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