Line references

The codes the railway describes itself in

An Engineer's Line Reference names a stretch of track, and a position along it is given in miles and chains from that line's own zero point — SPC1 72m 06ch, say. Every route this site plans reports the ELRs it runs over, and every station lookup shows where that station sits on them. This page is where those codes lead.

• Where a line goes — its track drawn on the map, with the lines it meets at junctions faint underneath, so you can follow the network code by code.
• What is on it — every mileposted position in order, stations and junctions and yards alike, each linking to its own station page.
• What kind of railway it is — electrification, top line speed, and how much of it runs in tunnel or over structures.

Two unrelated sources are joined here, and neither covers the other completely. Track geometry and its tags come from OpenStreetMap; mileposts come from Network Rail's TPS export. About 660 references have track but nothing mileposted on them, and about 80 have mileposts but no track we can draw — both are listed, with whichever half exists. Line names are contributed to OpenStreetMap rather than official: no industry source names an ELR at all, and a name can cover several of them, which is why the code is always shown too.

A name is not an identity, and a code cannot be decoded

Two habits will mislead you here, and both are worth unlearning early. The first is treating the name as the thing: "West Coast Main Line" spans sixteen separate ELRs, because a railway is referenced in engineering sections rather than in the routes a passenger would recognise. Ask for a line by name and you are asking about a stretch of it.

The second is reading meaning into the letters. MLN1 is Paddington to Plymouth — the Great Western, not the Midland, which is SPC1. The codes grew out of the pre-nationalisation companies and successive re-organisations, and any scheme that infers a route from the letters will be wrong often enough to be useless. Match on the code exactly, and read the endpoints to know where you are.

Two different measurements of length

Each line shows both a track distance and a mileposted extent, and neither is derived from the other. The first adds up every piece of track carrying the reference — the up road, the down road, the loops, the goods lines and the sidings. The second is simply the distance from the lowest milepost to the highest.

They differ by more than you would expect. MLN1 carries about 1,028 kilometres of track over a 244-mile extent, roughly two and a half times, because a four-track main line with relief roads and yards holds far more rail than its length suggests. A quiet single-track branch sits close to parity. The ratio is a fair shorthand for how heavily built a line is.

Most mileposted positions are not stations

The railway mileposts everything it needs to locate: junctions, signal boxes, loops, level crossings and depot exits are all recorded the same way a station is. On MLN1 there are over a hundred positions, and on SPC1 fewer than half carry a station code at all. The list shows them in order along the line because that is the order they exist in, with a filter for the stations if that is what you came for.

Positions are given in miles and chains — eighty chains to the mile — and truncated rather than rounded, so a position reads as the milepost you would actually pass. Rounding produces a table that appears to go backwards.

Guide: what an Engineer's Line Reference actually is — the same subject at length, including where the codes came from, how the two sources behind this page disagree, and why a single line can come back as hundreds of separate chains of track.