Network Rail will continue a major programme of upgrades on the Portsmouth Direct Line later this month, with buses replacing trains between Havant, Fareham and Portsmouth Harbour.

The work will take place from Saturday, March 28 to Thursday, April 2 while engineers carry out signalling and track improvements.

The latest phase includes an additional £120 million investment in the Portsmouth Direct Line as part of a multi-year programme to modernise the route.

When the full programme is completed in 2028, signalling will transfer from the Havant Area Signalling Centre to the Basingstoke Rail Operating Centre.

Network Rail said the change will improve communication between signallers and allow a faster response to incidents, helping to deliver a more reliable railway.

The work follows the first phase of the programme in 2025, when £129 million was invested to upgrade signalling between Farncombe and Petersfield to improve the reliability and safety of services between London and Portsmouth.

Engineers will upgrade the signalling system and strengthen key infrastructure in the Havant and Portsmouth area during the six-day closure.

Work will include repairs to cable troughing between Farlington and Cosham to protect signalling equipment, structural repairs to Portcreek Viaduct connecting the mainland with Portsmouth on the Isle of Portsea, and the renewal of 48 wheel timbers through platform two at Portsmouth & Southsea station.

A further 14 wheel timbers will be replaced outside Portsmouth Harbour station, and tamping work will be carried out using a machine that lifts and moves track to improve alignment through the Portsmouth area.

In total, engineers will complete about 1,378 hours of work during the closure. Train services will change while the work takes place.

South Western Railway services to and from Portsmouth Harbour will start or finish at Havant or Fareham.

Southern services to and from Portsmouth Harbour will start or finish at Havant, with services to Portsmouth & Southsea running instead to Bognor Regis. Southern trains between Brighton and Southampton will run as normal.

Great Western Railway services to and from Portsmouth Harbour will start or finish at Fareham.

Replacement buses will run five times an hour between Havant and Portsmouth Harbour, calling at Bedhampton, Hilsea, Fratton and Portsmouth & Southsea, and twice an hour between Fareham and Portsmouth Harbour, calling at Portchester, Cosham, Hilsea, Fratton and Portsmouth & Southsea.

Tom McNamee, infrastructure director speaking on behalf of Network Rail and South Western Railway, said: “Following the successful completion of the first phase of upgrades last year, we are now starting the next stage of modernising signalling on the Portsmouth Direct Line.

“Some of the signalling equipment in the Havant area is ageing and is increasingly prone to faults. Replacing it with modern technology will improve reliability and help reduce delays for passengers travelling to and from the south coast.

“Some of this work can only take place when trains are not running, so access is carefully planned to complete as much of the improvements as possible while minimising disruption.”

Further closures are planned around the late May bank holiday, with engineers expected to return again in the autumn. More details will be announced closer to the time.

More information about the Portsmouth Direct Line upgrade is available at the Network Rail website.