A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
| ELR | Route | Section | Remarks |
|---|---|---|---|
| KBC | Kingsbury Branch | Kingsbury Branch Jn to Baddesley Colliery GF | Known anomalies with data source accuracy |
| KBF | Kelloe Access Line Jn to Kelloe Bank Foot | Understood to be disused | |
| KBS1 | Kirkham to Blackpool South Line | Kirkham North Jn to Blackpool Central (Coastal Route) | Understood to be part closed |
| KBS2 | Kirkham North Jn to Blackpool South (Direct) | Understood to be disused | |
| KCH1 | Killoch Colliery Branch | Annbank Jn to former Drongan Jn | |
| KCH2 | Killoch Colliery Branch | former Drongan Jn to Killoch Colliery (NR boundary) | |
| KCS1 | Crewe Branch | Kidsgrove Jn to Crewe South Jn | |
| KEB | King Edward Bridge South East Curve | King Edward Bridge East Jn to King Edward Bridge North Jn | |
| KES | Knottingley Fork | Knottingley East Jn to Knottingley South Jn | |
| KGC | City Lines | Kensal Green Jn to Willesden | |
| KGW | Kensal Green Curve | Kensal Green Jn to Willesden New Station | |
| KHL | Kirkhill to Cathcart Line | Newton Kirkhill Jn to Cathcart West Jn | |
| KID1 | Kidwelly Branch | Kidwelly Junction to COM | Understood to be disused |
| KID2 | Kidwelly Branch | Kidwelly | Understood to be disused |
| KIL1 | Killingholme Branch | Immingham West Jn to Humber Road LX | |
| KIL2 | Killingholme Branch | Humber Road LX to End of Line | |
| KIL3 | Killingholme Branch | Goxhill Jn to East Halton | Understood to be disused |
| KJE1 | Keymer Jn to Eastbourne | Keymer Jn to former Southerham Jn (Lewes) | Short mile noted in records |
| KJE2 | Keymer Jn to Eastbourne | former Southerham Jn to Southerham Jn (Lewes) | Short mile noted in records |
| KJE3 | Keymer Jn to Eastbourne | Southerham Jn (Lewes) to Eastbourne | |
| KJW | Kingsbury Jn to Whitacre West Jn | ||
| KMG1 | Kingmoor Yard | Kingmoor Jn to Kingmoor Yard - for Up Reception (via Goods Lines) | |
| KMG2 | Kingmoor Yard | Kingmoor Yard (for Up Reception) to Mossband Jn (via Goods Lines) | |
| KNE1 | Stirling to Dunfermline | former Kincardine Jn to Elbowend Jn | |
| KNE2 | Stirling to Dunfermline | Elbowend Jn to Charlestown Jn | |
| KSH | Knockshinnoch Branch | Bank Jn to Knockshinnoch | Understood to be part closed |
| KSL | Leicester and Burton Line | Knighton South Jn to Leicester Jn | |
| KWD | Kingswinford Branch | Kingswinford South Jn to Pensnett | Understood to be disused |
| KWS | Knottingley West Jn to Shaftholme Jn | ||
| KYL | Kyle Line | Dingwall Jn to Kyle of Lochalsh |