Speeding motorists using Dublin's Port Tunnel will be caught using a new safety system that tracks their average speed through the urban motorway.
Special cameras will note the registration plate of the vehicle entering the tunnel, and when it emerges at the other end a computer will calculate if it has broken the 80kmh speed limit based on the time taken to travel through.
The system, which goes live in the autumn, will result in drivers caught breaking the limit being hit with an €80 fine and getting three penalty points.
It is being introduced because of the growth of traffic in the tunnel, which currently handles 24,000 vehicles a day.
The move was announced by Transport Infrastructure Ireland (TII) and An Garda Siochana, who said it would be the first average speed camera enforcement system in Ireland.
It is commonly used in other European countries.
"We welcome this enhancement to the operations of the Dublin Port Tunnel," said Chief Supt Aidan Reid of the Garda National Traffic Bureau.
"Due to an increase in traffic travelling through Dublin Port Tunnel, this new enforcement system provides additional support towards maintaining a safe travel experience for all users."
Traffic levels through the tunnel have increased by 40pc over the past five years, which means that statistically there is a greater chance of accidents.
Research suggests that use of the average speed detection system can reduce collision rates by as much as 50pc.
The average speed is calculated from the position of cameras at the mouth of the tunnel. It should take around 3.3 minutes to travel the 4.5km.
Once the system determines that a vehicle has exceeded the speed limit, it will automatically create a record of the violation which will then be transmitted to gardai.
Transport Infrastructure Ireland said the average speed was recorded between two camera positions covering all lanes.
This means that switching lanes will have no effect on average speed monitoring.
TII chief executive Michael Nolan said: "An average speed camera enforcement system will assist in maintaining the Dublin Port Tunnel's strong safety record.
"TII is grateful to An Garda Siochana for supporting us with this operational improvement."
Drivers will notice large yellow poles with cameras being installed from today.
These poles will support the average speed camera enforcement system, and testing is expected to begin soon.
The system will most likely go live in September or October.
The system will not have flashing lights or other operational indications, but it will be monitoring at all times when the tunnel is open.
Drivers who receive the fixed charge fine of €80, together with three penalty points, have 28 days to pay.
If not paid, the fine increases to €120 which also must be paid within 28 days.
If after this time (56 days) the fine is not paid, the offence is referred to the courts where five points will be applied and a maximum fine of €1,000 can be imposed.
The Dublin Port Tunnel opened in December 2006 and forms part of the M50 ring road around the city.