Hertford loop line

The Hertford loop line (also known colloquially as the Hertford Loop) is a branch of the East Coast Main Line, part of the Northern City Line commuter route to London for Hertford and other Hertfordshire towns and an occasional diversion route for the main line. The line is part of the Network Rail Strategic Route 8, SRS 08.03 and is classified as a London and South East Commuter line.

Hertford loop line
Great Northern Class 717 at Gordon Hill
Overview
Status	Operational
Owner	Network Rail
Locale	Greater London East of England
Termini	London Moorgate Stevenage
Stations	11
Service
Type	Heavy rail
System	National Rail
Services	1
Operator(s)	Great Northern
Depot(s)	Hornsey EMUD
Rolling stock	Class 717 "Desiro City"
History
Opened	1871—1924
Technical
Line length	24 mi (39 km)
Number of tracks	2
Track gauge	1,435 mm (4 ft 8+1⁄2 in) standard gauge
Loading gauge	W9
Route availability	RA 7-9
Electrification	25 kV AC OHLE
Operating speed	Maximum 75 mph (121 km/h)
Route map (Click to expand)

Hertford Loop Line
East Coast Main Line to Edinburgh Waverley Stevenage Langley South Junction Watton-at-Stone Stapleford Mole Wood Tunnel 364 yards (333 m) Hertford East branch line Hertford North Hertford & Welwyn Jn Rly Hornsmill Viaduct Bayford Ponsbourne Tunnel 1 mile 924 yards (2,454 m) Cuffley Sopers Farm Viaduct M25 Crews Hill Rendlesham Viaduct Gordon Hill Enfield Chase Enfield Grange Park Winchmore Hill Palmers Green Bowes Park Wood Green North Jn Bounds Green TMD Alexandra Palace Palace Gates Line East Coast Main Line to London King's Cross

History

The line was opened in three stages between 1871 and 1924. The first section called the Enfield Branch Railway was developed by the London and York Railway and went from Wood Green to Enfield. In 1898, a plan was approved to extend the line north to Hertford and Stevenage, in order to relieve congestion on the main line without having to widen the Welwyn Viaduct. Work started in 1905 and Cuffley was reached on 4 April 1910. The construction of two major viaducts and the Ponsbourne Tunnel (at 2,684 yards or 2,454 metres, the longest in the eastern counties of England and the last to be built by traditional methods), combined with World War I shortages of men and materials, delayed the opening of the route to Stevenage until 4 March 1918. Then it was single track and for goods services only. The line finally opened to passengers on 2 June 1924 when a new station at Hertford North was opened. The line was electrified in 1977.

The line was also used frequently during the Second World War as the Welwyn/Digswell Viaduct was at high risk from bombs.

Route and settlements served

The Hertford Line leaves the East Coast Main Line at Langley Junction, just south of Stevenage.

• Watton-at-Stone, serving the village of Watton-at-Stone
• Hertford North, serving the town of Hertford
• Bayford, serving the villages of Bayford and Brickendon
• Cuffley, serving the villages of Cuffley, Northaw and Goffs Oak
• Crews Hill, serving the village of Crews Hill
• Gordon Hill, serving Gordon Hill and Forty Hill, also close to Chase Farm Hospital.
• Enfield Chase, serving Enfield Town
• Grange Park, serving Grange Park
• Winchmore Hill, serving Winchmore Hill
• Palmers Green, serving Palmers Green
• Bowes Park, serving Bowes Park, Bounds Green and Wood Green

It rejoins the East Coast Main Line at Wood Green South Junction, north of Alexandra Palace.

Operations

Great Northern operates suburban services along the Hertford Line between London King's Cross or Moorgate, and Stevenage, Watton-at-Stone or Hertford North. Occasionally, London North Eastern Railway, Hull Trains, Grand Central, Lumo, Thameslink and other faster Great Northern services operate non-stop along the route when diverted off the main section of the East Coast Main Line, due to incidents or planned engineering work. There is a reversing siding to the north of Bowes Park which is occasionally used to reverse London North Eastern Railway trains heading for Bounds Green Depot. There are also bay platforms at Hertford North, Stevenage, and Gordon Hill, the latter acting as a terminus during peak hours and night only.

Infrastructure

The line is about 24 miles (39 km) long, is double track throughout and is electrified at 25 kV AC using overhead line equipment. It has a loading gauge of W9 and a maximum line speed of 75 mph (121 km/h).

Grade-separated junctions connect each end of the northbound track with the main line. All stations are long enough to accept two three-car (20m) EMUs. Not all stations are long enough for newly introduced 6-car EMUs, but their walk-through design allows for access.

Tunnels and viaducts

Major civil engineering structures on the Hertford Line include the following.

Tunnels and viaducts on the Hertford Line

Railway Structure	Length	Distance from London King's Cross	Location
Molewood Tunnel	364 yards (333 metres)	20 miles 31 chains – 20 miles 14 chains	North of Hertford North station
Hertford Viaduct	14 chains	19 miles 15 chains – 19 miles 01 chains	Between Hertford North and Bayford stations
Hornsmill Viaduct (River Lea)	6 chains	18 miles 58 chains – 18 miles 52 chains
Ponsbourne Tunnel	1 mile 924 yards (2454 metres)	16 miles 21 chains – 14 miles 59 chains	Between Bayford and Cuffley stations
Sopers Farm Viaduct	6 chains	12 miles 43 chains – 12 miles 37 chains	Between Cuffley and Crews Hill stations
Rendlesham Viaduct	7 chains	10 miles 40 chains – 10 miles 33 chains	Between Crews Hill and Gordon Hill stations
Down Enfield Viaduct (Down line)		5 miles 22 chains	North of Alexandra Palace station

ERTMS trials on the Hertford loop line

Network Rail used Beacon Rail owned Class 313 unit 313121 as a test vehicle for ERTMS on the Hertford Line. The plan involved resignalling a 5+1⁄2-mile (8.9 km) section of the double track route to allow existing passenger and freight services to work bi-directionally over the up Hertford loop line, freeing the down line for ERTMS tests and evaluation.

References

Hornby, Frank (1995) London Commuter Lines. Volume 1: Main lines north of the Thames. Kettering: Silver Link Publishing Ltd.