Bus drivers are threatening to withdraw services from areas of Belfast where they have been attacked.
The warning comes after a driver was robbed at knifepoint and another was injured after his vehicle was rammed by joyriders.
Michael Dornan, chairman of the Unite union said staff at Translink, which operates the public transport network, were outraged by the violence.
He said: "We will not tolerate needless attacks on drivers, if the community leaders from those areas cannot provide us with assurances of our safety while serving the people of that community, then we will pull back from that area or any area that can not control this needless antisocial behaviour, as someone could have been very seriously injured."
Last night a bus driver and passengers escaped serious injury after a stolen car smashed into their vehicle at Suffolk Road in west Belfast at about 8.55pm. The blue car believed to have been involved in the collision was later recovered at Falcarragh Drive.
Police said it had been abandoned by two men and a woman.
In a separate incident a short time later, another driver was left badly shaken after a man wearing a hoodie and carrying a knife boarded a bus near Forthriver Road in north Belfast and stole the cash box.
Mr Dornan said bus drivers wanted to get on with the job of providing a valuable service to the communities in which they were attacked.
He urged anyone with information to contact the Police Service of Northern Ireland (PSNI).
A police spokeswoman confirmed they were investigating both incidents and appealed for any witnesses to come forward.