Engineer's Line Reference

An Engineer's Line Reference (ELR) is a three alpha, or four alpha-numeric, code used to uniquely identify a section of track on the main-line railway of Britain owned, or maintained, by Network Rail.

An ELR is formed of a minimum of three upper-case letters identifying the route, normally using acronyms or abbreviations of the names of the primary locations (junctions or principal railway stations) they connect. For example, XTD is the section of railway between Charing Cross station to Dover station, and VTB is the section of railway between Victoria station to Brighton station. To ensure uniqueness, and convey local geographic (rather than railway principal junction or station) naming convention, an ELR may be formed of commonly-referred nomenclature, e.g. NKL is the section of track between North Kent East Junction and Dartford Junction, but is more frequently referred to as the North Kent Line (hence, the ELR).

A mandatory requirement of an ELR is that the mileage within it must be unique. Where a section of track is made up of several pre-existing routes, or where a mileage changes or reversal is present, the ELR is suffixed with a single digit (1 to 9). For example, the East Coast Main Line route from London King's Cross station to Edinburgh Waverley station is formed of ELRs ECM1 (King's Cross to Shaftholme Junction) through to ECM9 (Edinburgh Waverley station) with intermediate ELRs of ECM2, ECM3, ECM4, ECM5, ECM6, ECM7 and ECM8.

Location designator painted on a railway overline bridge, showing miles and chains

As the mileage within an ELR cannot be duplicated, any main-line railway location on Network Rail owned, or maintained, infrastructure can therefore be uniquely identified by a combination of ELR and mileage. For example, EJM 13M 16ch refers to Plessey Road level crossing on the Earsdon Junction to Morpeth North Junction (hence the ELR of EJM). The bridge shown in the associated photograph is located at 112M 63ch on ELR MLN; this ELR has subsequently been superseded by ELR MLN1, Paddington - Bristol - Penzance (Paddington - Change of Mileage - Plymouth Station West).

As at 2020, there were a total of 1,595 ELRs on Network Rail infrastructure.

An authoritative public domain reference to ELRs is available on Phil Deaves' Engineers' Line References page.

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