Train drivers are calling on Scotland's transport minister to intervene over concern about anti-social behaviour on some services out of Glasgow.
The ASLEF union said Humza Yousaf had to act to protect passengers and staff on services to Helensburgh and Balloch.
British Transport Police said it had stepped up patrols along the route.
Mr Yousaf said he had committed his support to a campaign which aims to protect transport workers from acts of violence.
ASLEF said its members were ready to refuse to work on the line because of the violence and anti-social behaviour "plaguing" passengers and staff.
Union organiser Kevin Lindsay said: "There are real concerns that a member of the public, or a rail worker, is going to get seriously injured or worse.
"Our members are sick and fed up and getting ready to refuse to work on these services. So an urgent response is now needed before a community loses its rail services and, more importantly, a rail worker is seriously hurt or worse."
Mr Lindsay said it was "imperative" that the transport minister took urgent action to ensure the safety of passengers and rail staff.
The union is calling for every train on the route to have at least two members of staff on board, with increased support from the British Transport Police.
It also said its members were seeking advice on using the law to take action against individuals, the local council, Scottish government and ScotRail over the attacks.
Mr Yousaf said: "Anti-social behaviour at rail stations and violence or the threat of violence against those using and working on public transport is wholly unacceptable.
"Every worker and passenger has the absolute right to go about their business without the fear of verbal or physical assault.
"We work closely with the police, Scotland's transport providers and the trade unions to raise awareness of this issue, and I have already committed my support in terms of the 'Violence against Transport Workers' campaign."
Scotrail said that from Friday, the British Transport Police would have four officers on patrol at the station and on the route.
They also said that they were due to meet with community leaders and police to find a "long-term solution" to the issue.
The British Transport Police said it was working to identify and prosecute offenders.
Ch Insp Davie Gray said: "In recent weeks, we have stepped up our patrols on this stretch of the line in order to deter and detect criminality and anti-social behaviour.
"The public and rail staff should be reassured that we are taking positive and firm action against trouble makers.
"A number of arrests have been made and we will continue being highly visible both on board train services and at Helensburgh and other stations."