Engineer's Line Reference

An ELR is formed of a minimum of three upper-case letters identifying the line, normally using acronyms or abbreviations of the names of the primary locations (junctions or principal railway stations) they connect.

For example, XTD is the South Eastern Main Line running from Charing Cross via Tonbridge to Dover Priory.

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 railway line between North Kent East Junction and Dartford Junction, but is more frequently referred to as the North Kent Line (hence, the ELR).

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).

As at 2023, there were a total of 1,590[2] Engineer's Line References listed within the Network Rail infrastructure geospatial model.