ScotRail passengers are warned of threatened disruption after the RMT union today announced an indefinite overtime ban from Wednesday 10 October
It follows an overwhelming majority of conductors and other staff voting for the action over being paid less than drivers for working on days off.
The union has instructed its 3,500 members involved not to volunteer for overtime or work on "rest days" from midnight on 10 October "until further notice".
It has said this would cause "massive" disruption because ScotRail is short of staff.
RMT Scotland organiser Mick Hogg said: "Our railway will come to a grinding halt if overtime is banned - no question about this."
BACKGROUND: RMT warns ScotRail will 'grind to halt' after vote to ban overtime
General secretary Mick Cash said: "It cannot be right that the company seem to value one group of workers over another.
"Their approach to the rest day working payments, where they have offered driver grades enhanced arrangements is nothing short of discriminatory.
"A driver working rest days is no different than any other member of front line staff working rest days.
"All staff should be treated equally and fairly."
The union is holding a separate ballot among train maintenance staff.
Train conductors and other RMT members such as station staff are paid between £112 and £140 for working their rest days compared to £300 for drivers.
Angus Thom, ScotRail chief operating officer, said: “ScotRail is investing more than £4 million in 140 new front-line roles to improve the work-life balance of our people and provide a better service to our customers.
"This investment means more people employed by ScotRail and will significantly reduce the need for rest day working.
“We are disappointed by this decision, but we will continue to work with our people and their trade union representatives on this.”