Probabilistic Gauging – First of a Kind Project

Theoretical average clearance improvement in the lower sector by through the use of Probabilistic Gauging.
Theoretical intervention cost savings through the use of Probabilistic Gauging over the WHL Class 153 cycle car introduction.
Theoretical foul passenger platforms removed from scope through the use of Probabilistic Gauging.


DGauge have previously developed probabilistic methods of gauging as part of the RSSB / Future Railways challenge examining the Avoidance of Bridge Reconstruction. The technology developed as part of this project was awarded RIRL Level 6 status (Operational Transition) by Network Rail’s Product Development Panel.


As part of the funded SBRI Rail First of a Kind Round 3 Innovate UK Competition, DGauge aimed to demonstrate that the space on the UK rail network could be maximised by improving the way in which gauging is undertaken, and that significant cost savings could be achieved as a result, while developing the Probabilistic Gauging methodology to RIRL7.

Our Process

Absolute Gauging:

Absolute Gauging is the standard gauging methodology which calculates the clearance between vehicles and structures based on the vehicle model, track conditions and measured structure profile. Each of these are made up of several parameters assumed to be independently and simultaneously at the limits of their allowable variation (worst case scenario). These are aggregated together resulting in the worst case clearance at a location.

Probabilistic Gauging:

The Probabilistic Gauging on the other hand is an innovative gauging method which considers both the magnitude and the likelihood of selected variables within the gauging process. Unlike Absolute Gauging, which takes a conservative approach to clearance calculation, Probabilistic Gauging undertakes a clearance simulation that combines all the gauging variables statistically to define the exceptional clearance. This allows us to understand what real-world clearances may occur between the vehicle and infrastructure. This process can provide a risk-based approach to gauging which may be used to minimise maintenance or avoid costly infrastructure works. Through this project DGauge developed Probabilistic Gauging further to RIRL7 certification.

Case Study (Network Modelling):

To demonstrate the benefits of using Probabilistic Gauging DGauge modelled the West Highland Line using the very latest survey data comprising all railway infrastructure including, but not limited to: overbridges, tunnels, underbridges, signalling equipment, platforms and awnings. DGauge dynamically modelled the vehicle to consider variable passenger loading and undertook thorough independent checks on survey data, identifying cases where unrealistic information leads to false gauging issues and investigated the possibility of correcting the errors. Traditional Absolute Gauging assessments were undertaken and structures with close clearance were assessed using Probabilistic Gauging.

Theoretical Clearance Benefits:

Probabilistic Gauging used on the West Highland Line demonstrated an average clearance improvement of 34mm in the lower sector (typically platforms) and 30mm in the upper sector (typically tunnels or overbridges).

Theoretical Cost Benefits:

Infrastructure modifications previously calculated with NR using absolute methods amounted to approximately £9.8million. Through the use of Probabilistic Gauging, the number of structures where intervention works were required was reduced by 90. As a consequence, this reduced the infrastructure modification costs to £1.8million by comparison.

As part of this project Probabilistic Gauging was awarded with RIRL Level 7 status and is now included within the suite of gauging assessments provided by DGauge.

“Our team members were able to smash our goals quicker than we did before”

Annabelle Porter,
Customer Service Officer

“Our team members were able to smash our goals quicker than we did before”

Annabelle Porter,
Customer Service Officer

Success Stories

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