Speed cameras in the Port Tunnel have not gone live yet.
The cameras and software were installed at the entrance and exit last year.
They record the time the car goes into, and exits the tunnel to work out if motorists are breaking the 80 kilometre limit.
The "time over distance" system works out the average speed cars and trucks are doing along the 4.5km stretch.
The cameras were due to go live in recent weeks and it's unclear when this will happen.
According to Transport Infrastructure Ireland, more than half of all vehicles using the tunnel break the speed limit.