They say the road, while internal, is used by general traffic including cars, ambulances and even articulated trucks and a potential accident could pose serious problems.
And there are plans to put three double-decker bus services on the thoroughfare, a proposal which has caused serious alarm, local man Benny Usher told the Herald.
Mr Usher, who lives on Ardmore Drive, which backs onto the northside hospital's grounds, said the road is a metre above his garden level but two metres higher than a neighbour's garden.
"Our quality of life is gone. People are afraid to let children into the garden," he said.
Apart from being overlooked by passing traffic, they are very concerned that if a vehicle was involved in an accident on the road it could come over their back walls.
The road rises to within a couple of feet from the top of garden walls and is only inches from property boundaries.
Mr Usher said Beaumont usually inform residents when they are making a planning application.
"The application was posted on the gates of the hospital, half a mile away. Before that they let us know about building projects. They didn't let us know about this one which has had a terrible impact on our lives," he added.
Mr Usher believes there are plans to run three buses on the route. "If a double-decker bus overturns, it could go into somebody's garden," he said.
Fine Gael's Gerry Breen said there is an admission on behalf of the hospital and Dublin City Council that there is a problem.
"The road is only five feet or less from the back gardens. You could get a stray vehicle and the next thing it is in over somebody's wall," the councillor added.
Other complaints include noise pollution and health issues arising from vehicle fumes.
Beaumont Hospital, however, says it was necessary to realign an internal road as part of the construction of the new psychiatric unit, for which the hospital was granted planning permission in 2011.
It has "engaged proactively" with residents to limit the effects of the realigned road, it insists.
The hospital says that it is working with its building suppliers so that they use the back entrance to the campus at Trim Road, thereby moving heavy traffic away from residents.