scope:

This Network Rail standard specifies the requirements for the reinstatement of ATG track with line speeds up to 125 mph where class 221 and 390 tilting vehicles operate. This includes:

a. the construction of new sections of track, and routes

b. the replacement of contiguous lengths of track components or S&C layouts, either singly or in combination, as part of project or renewal activities

c. the replacement or new construction of drainage, level crossings, platforms, bridges or other track features

d. the requirements for the design of track geometry for both newly installed and existing track

This standard applies to those who specify, design or supervise the installation of new track and those who design alignments on existing track.

Purpose

Absolute Track Geometry (ATG) is a defined alignment design that is reinstated when the track is disturbed by track maintenance, track renewal or other work. This is to comply with the safety case for Enhanced Permissible Speed (EPS) where titling vehicles operate which mandates ATG.

This procedure defines how Infrastructure Projects (IP) and other approved suppliers:

• Manage the reinstatement of the ATG track alignment for plain line and Switch & Crossing (S&C)
• Will manage changes to the ATG Design
• Design track adjacent to ATG alignments

Risks associated with not reinstating the Track to ATG include:

• Train collision due to failing passing clearances if ATG geometry and / or position of the Through Alignment Design (TAD) are compromised.
• Derailment / Rollover on EPS routes where exceptional design values are applied.
• Losing track clearance position due to 'creep' from repeated application of maintenance tamping