The South Western Railway (SWR) service came to a standstill after hitting part of a barrier between Hinton Admiral and New Milton.
Rail passengers have reacted with fury after seeing SWR apologise and post a photo of a barrier on social media.
One person said: “You haven’t closed the line for 4 hours because of that. Tell me this is a joke? Bmth station has about 800 people there.”
Another added: “So a 4hr line closure and still massive delays, because @NetworkRailWssx failed to secure the plastic chapter 8 barriers, and how much damage has this caused, and is the RAIB investigating this incident?”
Emergency services attended the scene, and response teams inspected the train before it was moved to Bournemouth depot at a reduced speed.
A spokesman for SWR said: “We’re sorry for the disruption to customers travelling this evening.
“A train struck part of a barrier between Hinton Admiral and New Milton, causing it to come to a stand and blocking the line.
“Colleagues from across the railway are working alongside the emergency services to safely assist passengers and reopen the line as quickly as possible.”
As a result of the incident, trains were unable to run between Bournemouth and Southampton Central while the failed train moved at a reduced speed to Bournemouth depot.
Services between Weymouth, Bournemouth, and London Waterloo were unable to operate between Bournemouth and Southampton Central, with delays, cancellations, and last-minute changes affecting other routes across the SWR network.
Train services resumed between Southampton Central and Bournemouth later in the evening, but SWR warned that ongoing disruption was likely until the end of the service.
Passengers were advised to check journey planners before travelling and to expect significant delays.
A range of alternative travel options were made available to affected passengers.
Tickets were accepted on CrossCountry services between Basingstoke and Bournemouth, and on various bus routes including Bluestar 11 and 12 between Southampton and Totton, and Morebus routes serving Lymington, New Milton, Christchurch, Branksome, Parkstone, Poole, Hamworthy, Wareham, and Salisbury.
SWR also allowed passengers to book taxis and claim the fare back for journeys between any stations served by SWR from Basingstoke to Weymouth.
Passengers were asked to retain train tickets and taxi receipts to support reimbursement claims.
SWR tickets dated Saturday, August 1 can be used to travel on Sunday, August 2 between Weymouth and London Waterloo only.
Passengers were encouraged to speak to a member of staff or use a station help point if they needed further assistance.