First Great Western (FGW) rail workers in the RMT union are set to launch another wave of industrial action from next weekend.
The union is in dispute with FGW bosses over threats to jobs, services and safety stemming from the introduction of new intercity trains on the network.
Across the rail industry cuts are being pushed through to squeeze costs, boost profits and weaken union organisation.
All members, excluding maintenance workers, are set to strike for 24 hours on Sunday 23 August.
This is to be followed with a further two 24-hour walkouts by all members on 29 and 31 August.
Maintenance crew are also instructed not to work any overtime or rest days on 23 and 30 August.
A solid 48-hour walkout last month brought much of the network to a halt despite a desperate scabbing operation by bosses.
Resolver, a complaints-handling website, said that First Great Western is Britain’s most complained about train company.