New technology to catch speeding motorists in Dublin's Port Tunnel is due to go live shortly.

Drivers breaking the speed limit will be caught using a new safety system that tracks their average speed through the tunnel.

Any motorist completing the journey in less than three minutes and 30 seconds would be breaking the 80km/h speed limit.

Sean O'Neill of Transport Infrastructure Ireland (TII) said the new safety system in the tunnel is a fair one.

Speaking on RTÉ's News at One, Mr O'Neill said the 4.5km long tunnel has an excellent safety record and they want to maintain that.

"The tunnel is a contained environment. If accidents happen it is difficult to get to people and you always want to be careful when dealing with tunnels. It is a motorway, part of the M50, and you want people to drive through there safely."

The new system was announced last June by TII and the gardaí.

Speeding will result in automatic fines of €80 and three penalty points.

It will be the first average speed camera enforcement system in Ireland and TII said the cameras are already affecting driver behaviour.