Ambulances in Stockholm are testing a system that interrupts in-car audio systems to warn drivers that they need to get through. The solution was developed by students at the KTH Royal Institute of Technology in the city.
It broadcasts a voice warning, while a text message also appears in the radio display. It uses an FM radio signal to jam drivers' speakers and stop music playing.
It will only be able to alert cars that have their radios turned on. It can also interrupt CDs and music connected via Bluetooth.