Trains in Hertfordshire are set to be disrupted over the August bank holiday weekend due to work on a digital signalling system.

On Sunday, August 25, the first long-distance train will test the newly-installed system at high speed between Welwyn Garden City and Hitchin.

Under the new system, traditional lineside signals are being replaced with signalling displayed inside drivers' cabs. Trains will run using the new signalling from late 2025.

In the meantime, the railway in and around the affected section has to be closed while controlled testing is carried out.

From the evening of Saturday, August 24, until the morning of Monday, August 26, no LNER trains will run between Peterborough and London, meaning none will stop at Stevenage.

Thameslink and Great Northern trains will also be affected. There will be no trains between Potters Bar, Peterborough and Royston, and between Hertford North and Stevenage on Sunday, August 25.

Evening services from approximately 10pm on Saturday, August 24 and early morning services on Monday, August 26, until 9am, will be affected too.

Rail replacement buses will be in operation, and all passengers are advised to plan their journeys in advance and leave extra time.

The planned disruptions and alternative routes can be found below:

Sunday, August 25:

No trains will run between:

  • Potters Bar and St Neots
  • Potters Bar and Royston
  • Hertford North and Stevenage

A rail replacement bus service will run between:

  • Potters Bar and Hitchin
  • Hitchin and Royston
  • Hertford North and Stevenage
  • St Albans City and Stevenage via Hatfield
  • Luton Airport Parkway and Stevenage via Hitchin
  • St Neots and Bedford
  • St Neots and Hitchin 

Trains will run between:

  • St Neots and Peterborough
  • Royston and Cambridge/Kings Lynn
  • London King’s Cross and Potters Bar
  • Moorgate and Potters Bar / Hertford North

Saturday, August 24, from 10pm until end of service

No trains will run between:

  • Potters Bar and Hitchin
  • Potters Bar and Royston
  • Hertford North and Stevenage

Additionally, from 12:15am, no trains will run between:

  • Hitchin and St Neots

From 10pm, a rail replacement bus service will run between:

  • Potters Bar and Hitchin
  • Hitchin and Royston
  • Hertford North and Stevenage
  • St Albans City and Stevenage via Hitchin

From 00:15, a rail replacement bus service will also run between:

  • Hitchin and St Neots

Monday, August 26, from start of service until approximately 9am.

No trains will run between:

  • Potters Bar and St Neots
  • Potters Bar and Royston
  • Hertford North and Stevenage

A rail replacement bus service will run between:

  • Potters Bar and Hitchin
  • Hitchin and Royston
  • Hertford North and Stevenage
  • St Albans City and Stevenage via Hatfield
  • Luton Airport Parkway and Stevenage via Hitchin
  • St Neots and Bedford
  • St Neots and Hitchin 

Ed Akers, Network Rail’s industry partnership director on the £1.4bn East Coast Digital Programme, said: “The testing work will take us a step closer to the introduction of digital, in-cab signalling on the East Coast Main Line, which will improve services for passengers and create a more reliable and resilient railway.

“We have carefully planned this work to avoid the busiest times of the August Bank Holiday weekend, and where possible passengers may be able to avoid this disruption by travelling before or after Sunday, August 25.

"I want to thank those passengers who will be affected for their patience and understanding of this work”.

Chris Fowler, network operations and performance director for Govia Thameslink Railway which operates Thameslink and Great Northern trains, said: “With no trains running on a key section of our route between London and Peterborough and Cambridge this August bank holiday, it’s essential that our customers plan ahead and allow plenty of extra time.”

Testing and proving between Welwyn and Hitchin is expected to continue in the coming months, with different trains and onboard systems used. Most work will be conducted overnight to avoid affecting regular passenger services.