Motorists who overstay a five-minute pick-up and drop-off time limit at Perth Airport’s Terminal 2 will soon be slugged up to $18.

Perth Airport is testing new numberplate recognition technology designed to stop drivers using the pick-up and drop-off zones as a short-term carpark while waiting for disembarking passengers.

Drivers will have five minutes free, but longer stays will incur a parking fee starting at $6 for five to 10 minutes and rising up to $18 for drivers who stay 20 minutes.

Signs have been installed warning drivers of the new express pick-up and drop-off system, which is expected to go live before the end of the month. But there will be a grace period to educate drivers before the airport starts stinging overstayers.

Perth Airport insists the new charges are not fines and the express pick-up and drop-off parking fees are “no different from the procedure in place in our short and long-term carparks when vehicles stay longer than the allotted free period”.

The airport says the parking crackdown is needed to ease vehicle gridlock. Its traffic modelling shows a third of drivers are overstaying, leading to delays for other passengers being picked up or dropped off from T2 and also hampering access on Airport Drive and to Terminal 1.

As a no-cost alternative, the airport says motorists should park in any of the airport’s long-term carparks where the first hour is free, then wait for a call from the passenger when they are ready to be picked up.

“Motorists will be advised of the time they enter the zone and there will be a number of digital clocks so they can ensure they do not overstay,” a spokesman said. “The system will go through testing and there will be an additional communications period before it becomes fully operational.”

At Melbourne Airport, motorists get 10 minutes free in the pick-up and drop-off zone and those who don’t move on are slugged $8 for stays of 10-15 minutes up to $16 for 30-60 minutes.

At Sydney, the drop-off and pick-up zone has a one-minute maximum, otherwise motorists must park in a priority pick-up zone which costs $4.20 for stays up to 15 minutes, $8.40 for 15 to 30 minutes or $21 for 30 to 60 minutes.

The latest Perth Airport annual report shows its revenue from “ground transport services” — which includes carparks — was more than $85 million last financial year, double the $40 million it made a decade ago.

While motorists may begrudge the new charges, the most recent Australian Competition and Consumer Commission’s Airport Monitoring Report rated Perth Airport as Australia’s best major airport.

Regarding parking, the ACCC found that Perth Airport had the cheapest drive-up prices for short-term parking of any major airport and the lowest profit margin on parking. But it said all other major airports had multi-storey undercover parking linked directly to the terminals, unlike Perth.

Aside from parking fees, passengers who want a baggage trolley at Perth Airport must pay $4, while a locker to store baggage for up to 24 hours costs $10 to $14. Lockers cost $10 to $18 at Melbourne Airport and $12 to $16 in Sydney.

The new express parking fees come as Perth Airport is under fire from Qantas for price gouging. It made the accusations in a response to a writ lodged in the Supreme Court pursuing the airline for more than $11 million in unpaid charges.