A new system is being tested in Sweden which can interrupt in-car audio systems to warn drivers that an ambulance needs to get past.

The system was dreamt up by students of KTH Royal Institute of Technology in the city of Stockholm.

Alongside a voice warning, the radio displays a text message.

Speakers are jammed and music stopped through the FM radio signal.

Only cars with their radios turned on will receive the warning. Music being played through Bluetooth and on CDs can also be interrupted.

Ambulances send out the signal to nearby motorists using FM tuners which utilise RDS, a protocol which can embed small amounts of data within FM transmissions. This protocol is usually used to show a song’s title or the name of a radio station.

Mikael Erneberg, a KTH student who worked on the system, said: "Often drivers have only a few seconds to react and give way to emergency vehicles."

"The optimal warning time is at least 10 to 15 seconds."

Loud audio can block out the sound of sirens and, say the students, accidents related to drivers who have not heard ambulance sirens are increasing.

Mr Erneberg continued, "We want to catch motorists' attention at an early stage, and mitigate stress that impairs road safety."

"It fulfils three functions: improving accessibility for first responders, improving road safety and make the working environment in transport better for vulnerable professions," said Mr Erneberg.

A small number of ambulances and fire engines are set to begin testing the jamming system, which will roll out across Sweden later in 2017.

The invention can determine the most appropriate time to deliver the message, based on the speed of the traffic.