Plans to introduce a new "barnacle" parking fine system at a US university have been put on hold after complaints from students.
The so-called barnacle is a type of car clamp that sticks to the windscreen using suction cups, and releases its grip after the parking fine is paid.
But outraged students at the University of Oklahoma (OU) shared tips for removing it without paying.
The university's parking authority said it would delay its trial of the device.
"The amount of sheer rage festering in my body right now... this is what I'm in thousands of dollars of debt for? I pay how much to go here and you continue to exploit us in ludicrous ways for profit?" said one student on Twitter.
The university had originally said the scheme would be more "convenient" for students and less expensive than towing away vehicles.
If a driver had failed to pay more than three outstanding fines, a parking warden would attach the barnacle to the windscreen.
The large plastic screen would be held in place with powerful suction cups, and obscure the driver's view.
Driving off with the device attached to the car would sound an alarm and alert the parking warden.
Students would be able to pay their parking fine in an app to release the barnacle, and then return the device to a drop box in the car park.
Barnacle chief executive Kevin Dougherty told the BBC that the device was only used when drivers had parked illegally or failed to pay parking fines.
He said it was not stuck "randomly" on innocent drivers' vehicles, and he said those who had parked illegally would now face the hassle of being towed.
Several students had complained about the planned trial, and said they had found inventive ways of prising off the barnacle from their cars without having to pay.
One poster on social news site Reddit claimed he had been able to extract a mobile network Sim card from one of the devices, and used it to access the internet for free.
Mr Dougherty said improvements had since been made to the design of the barnacle, and said 40,000 had been deployed and returned without incident.
Campus newspaper the OU Daily said the trial had been suspended (link geoblocked in the EU) while the parking team sought "further input from the OU community".
The university had been renting five of the devices for use on campus.
It said students would be given 30 days' notice if it decided to reintroduce the barnacle system.