Motorists left behind more than €300,000 at toll booths last year after driving away without change when passing through a motorway plaza.
Transport Infrastructure Ireland (TII) toll booths generated nearly half a billion euro in 2025 with the chronically congested M50 accounting for more than 40% of the total.
TII also revealed that there was €445,000 worth of unpaid tolls nationwide last year although they refused to provide a breakdown of which roads were most problematic on security grounds.
The transport operator said a further €5.93 million of bad debt was written off on M50 tolls, according to records released under FOI.
The Dublin ring road - despite its reputation for almost daily gridlock - continues, however, to be a cash cow, generating €216.6 million in toll revenue last year.
Payments for use of the M1, which connects the capital to the border, totalled €52.4 million in 2025.
Motorists left around €102,000 in tolls behind when travelling on that motorway, TII data showed.
The M4 motorway, linking Dublin with the west, generated €49.45 million in toll revenue with just €9,000 in overpayments.
The next highest earning road was the Dublin Port Tunnel, where motorists forked out €35.4 million for a shortcut in and out of the city centre.
Around €27,000 in overpaid tolls were left behind by motorists.
The Limerick Tunnel generated almost €31 million in income for its operators with overpayments of around €31,000.
Both the M3 and the M7/M8 brought in roughly €29 million in toll income with around €65,000 in change left behind in plaza buckets.
Toll revenue of €15.62 million was reported on the N6, €24.7 million on the M8, and €14.6 million on the N25.
Across the board, the use of electronic tolling systems or tags accounted for around two-thirds of all payments.
TII said that every plaza in the country had an option for people to receive exact change if they wished.
They said figures for the East-Link toll bridge in Dublin's Docklands area were not available as it was the responsibility of Dublin City Council.
A TII spokesman added: "The Government identified a role for Public Private Partnerships (PPPs) as a means of delivering critical public infrastructure.
"It was a Government policy decision to assist with the delivery of the new motorways.
"The revenues collected on these toll roads are collected by the relevant PPP company and are generally used … to repay loans borrowed to finance construction of the road and to fund ongoing operations and maintenance activities."
Reporting by Ken Foxe
