Transport Infrastructure Ireland is warning that the M50 around Dublin is becoming a 'rat run'.
The route has been recording 10% annual growth over the past few years.
TII spokesman Sean O'Neill says that because of connectivity to the port and other central points, if the M50 doesn't work well, 'the whole country's in trouble'.
And he says patterns in driver behaviour are posing problems.
"It's the major corridor in and around the city but it's becoming a rat run.
"Our stats are showing us that a lot of people are taking two junctions or less, so they're hopping on and hopping off.
"What that does is it creates a problem with the functionality of the road because people then are slamming on brakes, they're changing lanes, and then you get accidents.
"Once an accident happens on the M50 the whole thing stops," he said.