Sixty-five cars were seized last year for not paying Dublin’s M50 toll.
Figures from Transport Infrastructure Ireland (TII) show that more than 170 vehicles have been seized since the barrier-free system came into being in 2008.
The compliance rate is now at 97%, but a small number of motorists are travelling on the M50 three to four times a day without paying.
One serial offender who was prosecuted had to make a payment of more than €16,000 after making more than 1,200 trips without paying. In 2016, another offender had to pay more than €12,167 in fines.
A spokesman said: "These people are needlessly ending up in court and putting themselves at risk of incurring a criminal conviction, or having the debt registered against them as well as having their vehicle seized by the Sheriff.
"We are urging these people to contact eFlow in order to resolve their case before it gets to court."
TII’s Sean O’Neill said: "A significant amount of cars were seized in 2016, because the process does take a long time. People have to wrack up a lot of violations and there’s a court process (before cars are seized)."
TII provided a list of other cases, including:
M50 toll charges start at €2.10 for cars with a tag account. (Full list of charges here.)