Driving tests are due to resume in Northern Ireland - with additional measures in place to try and clear the backlog.
Testing was suspended four months ago this week when lockdown measures kicked in but gets underway again after 23 April - and demand is set to be high.
The estimate, based on the number of valid theory tests, is that around 22,000 people are waiting to pass their test.
Jeremy Logan from the Driver and Vehicle Agency said: "We probably lost somewhere in the region of 10 months of testing and that theory test figure, in terms of those who can take their driving test, will clearly increase now that the theory testing service comes back.
"But I like to think we would make a significant dent in those figures within the next six months, particularly over the summer period."
Those with theory tests that expire by the end of October can book a test from Monday.
Those with theory tests valid until March next year can book at the start of May, and from the middle of May, all others will be able to book in.
It's estimated nearly 9,000 people are in those first two groups.
Infrastructure Minister Nichola Mallon says additional examiners and extra testing centres are among some of the measures that can be used to help bring down the waiting list.
"We will continue to monitor that extremely closely and we have put in a number of additional capacity measures in place," the minister said.
"Whether test centres, additional examiners, extended opening hours and so forth - so we're constantly monitoring that to ensure we're maxmising our capacity."