Talks to avoid First Great Western rail strikes have broken down without an agreement being reached, a company negotiator said.
Walkouts by rail workers, which were announced on Monday, are still set to go ahead despite talks earlier between the train operator and the RMT union.
They were held in a bid to end a dispute over the introduction of new Hitachi Intercity trains.
Strikes are planned on 23 August and over the Bank Holiday weekend.
A negotiator for First Great Western said the talks were positive and more discussions would be held before the first strike took place.
A spokesman for the RMT union confirmed that the strikes were still set to go ahead.
Union members, including guards and platform attendants, will walk out for 24 hours on 23 August and for 72 hours from 29 August, while members who work on maintenance will strike on 29 August and 31 August.
All of the strikes will begin at 00:01 BST and end at 23:59 BST.
Railworkers held a 48-hour strike earlier this month over the same dispute, causing disruption to tens of thousands of commuters.
It affected high-speed services between London Paddington, south Wales, the Cotswolds, the Thames Valley region and the West of England.
The RMT union said it had received a “lack of assurances” over job protection for engineers.
It said it was concerned that the role of guards and platform staff would be diluted by plans for drivers to operate train doors, and criticised the proposed removal of buffet facilities.
A First Great Western spokesman said the new trains would have more seats and deliver faster and more frequent journeys for passengers.