The EU is proposing kit that renders the accelerator pedal temporarily unresponsive when the speed limit is reached.
The driver has to push hard on the pedal to de-activate the system and deliberately break the limit.
Car makers suggest the cheaper option of a bleeping light on the dashboard.
The issue will be debated at a meeting of EU technical experts on Thursday. Whichever system is chosen could apply in the UK, despite Brexit.
What's at stake?
Each side says their proposed system will annoy drivers less.
The safety experts say their tests show drivers are irritated by the bleep, so they’ll just turn the system off when they arrive at the car.
They say the smart throttle doesn’t annoy drivers so much.
Dudley Curtis from the European Transport Safety Council (ETSC) told BBC News: “We are concerned that the final outcome of this debate might be a weakened version of the system which has far lower life-saving potential.”
The car makers’ association ACEA maintains that it supports safety innovation too.