Speed camera operators may go on strike after voting for industrial action in a dispute over pay and conditions.
The Siptu members work for GoSafe, the company that runs the speed camera service for the State.
Siptu officials said they were due to meet on Monday to discuss their next move.
Some staff also allege that strict shift patterns leaves them with little choice but to carry a plastic bottle for use in toilet breaks.
Individual GoSafe drivers who have spoken anonymously to The Irish Times said they were employed on nine-hour or 11-hour shifts, most of which was spent in the van.
The Siptu union represents more than half of a workforce of roughly 70 staff.
"There's a very strong chance they'll serve notice of industrial action this month, if there's no resolution," said Siptu organizer Brendan Carr.
The union sought a pay rise and also claimed members did not have adequate breaks or toilet facilities.
He said that the dispute highlighted an unacceptable practice of Government departments issuing contracts to companies who refused to engage with the State industrial relations bodies.
A GoSafe spokesperson was not available for comment.