ALMOST £3 million has been lost in unpaid M50 tolls by Northern Ireland drivers in the last four years.
The M50 is Ireland's busiest motorway and it introduced a barrier-free toll in 2008.
It was introduced due to bottlenecks at the old booths.
Now, drivers using the tolled section are recorded by cameras, which use vehicle recognition technology to record number plates.
Motorists are encouraged to pre-register online and are charged £1.90 for a one-way toll. The cost is £2.80 if not registered and drivers must pay by 8pm the following day or face a fine.
There were more than 50m journeys on the M50 last year, bringing in £135m in tolls. About 1.4m of these were made by Northern-registered vehicles.
Unpaid journeys made by vehicles not registered in the Republic are passed to Euro Parking Collection.
New figures reveal that in 2018 and 2017, £445,000 was written off each year. In 2016, £623,000 was written off, a drop from £1m in 2015.
Transport Infrastructure Ireland said every tollable passage on the M50 was pursued for payment "where possible".
A spokeswoman said compliance levels were increasing among drivers from the north.
"This is down to increased public information activity in Northern Ireland and direct engagement with the tourism sector," she said.
