Glasgow subway workers have voted for a series of strikes later this month which will disrupt the service during major music events.
The 24-hour walk-outs will take place during Summer Sessions at Bellahouston Park on 21, 25, 27 and 28 June.
The Unite union says train drivers and station staff feel "totally devalued and ignored" because of working conditions, and are often working 10 hours beyond their contracts or being asked to take shifts at short notice.
Strathclyde Partnership for Transport (SPT) said it is looking at what the action means for rail services.
SPT director of transport operations Richard Robinson said: "While we are disappointed that Unite has chosen to take this action while we are still in active discussions, SPT remains committed to working with Unite to resolve all issues as we plan for future working arrangements for the subway."
Members of Unite voted by 97.5% for strike action, with 100 workers taking part.
Strike dates coincide with four outdoor gigs at Bellahouston Park – the Sex Pistols during the Punk All Dayer festival on 21 June, Sting on 25 June, Simple Minds on 27 June and Stereophonics on 28 June.
A continuous overtime ban will also be in place from 13 June.