It's being claimed some Dublin Bus drivers have had to urinate in bottles on the job.
The company's being asked to provide toilets for staff as routes have become longer.
Dermot O'Leary from the National Bus and Rail Union says drivers are continuing to be caught short.
"You can use your imagination, there have been headlines describing how some have had to resort to using bottles", he explained.
The union is calling for Dublin Bus to build driver-only toilets along some longer routes, give drivers time to use existing toilets at train stations and get agreement from some retailers to allow drivers use their facilities.
Dermot O'Leary went on to say that the union has "communicated the issue with the company" for the past number of years.
He explained that the problem is becoming worse as routes get longer and traffic congestion becomes heavier - leaving drivers behind the wheel for longer.
"If something isn't done, we could end up in a situation where services could be disrupted", he warned.