scope:

The Earthwork Asset Derailment Models apply to the assessment of generic failures; the specific type of slope failure is not explicitly considered. Rather, the Earthwork Asset Derailment Models assess the linkage between the failure of the Earthwork asset with particular characteristics and the probability of causing a train derailment.

Purpose

The Earthwork Asset Derailment Models assess an estimated quantitative probability that a generic or non-specific slope failure of any particular Earthwork asset will result in a train derailment. This probability is referred to as 'p(Derail | Fail) ' or 'pDF'. The models use the following inputs:

a) Earthwork asset slope properties: geometry and geology

b) Track properties: curvature and presence of switches and crossings

c) National averages of slope failures leading to train derailments.

Although the specific type of slope failure is not explicitly assessed, Earthwork Asset Derailment Models assess the linkage between the failure of the asset with particular characteristics and the probability of causing a train derailment.

The ultimate output of the model, p(Derail | Fail), is used within the wider context of the Earthwork asset criticality assessment - see CP5 Earthworks Asset Policy (Network Rail, March 2015) and NR/L2/CIV/086/Mod12.

The Earthwork Asset Derailment Models have been developed as a set of three models:

Soil Cuttings Derailment Model;

Rock Cuttings Derailment Model; and

Embankments Derailment Model.

The development process for all three models is reported in:

Earthworks CP5 Roadmap: Understanding Safety Risk - Development of Cutting and Embankment Safety Risk Models (Network Rail, April 2014)

Update to earthworks risk models: probability of derailment given earthwork failure (Network Rail, November 2016)

All three Earthwork Asset Derailment Models have been implemented as a single master spreadsheet-based tool:

Earthwork asset p(Derail | Fail) calculator v2 (Network Rail, June 2016).

This tool supersedes both the National Earthworks Risk Reduction Programme (NERRP) Phase 2 Safety Risk Model for Cuttings v01 10/08/2012 ("Cuttings Risk Model") and the Embankment Safety Risk Model Single Asset Tool ("Embankment Risk Model").