The emergalert, to be manufactured locally, activates when an emergency vehicle turns on its sirens.

Temporarily overriding FM and AM radio transmission the device sounds a tone and a verbal message to tell the driver to give way to the emergency vehicle.

Inventor and firefighter Don Wilkie said knowing stationary traffic could be a matter of life or death inspired him to come up with the idea six years ago.

But he needed the technical help of a Geelong radio engineer, who did not want to be named, to develop the invention which was patented last month.

``I went to a call years ago and as we were driving the truck was stuck for nearly two kilometres. As we went past one driver he had his window down and the officer with me said he must have been listening to the blooming radio too loud,'' Mr Wilkie said.

``It popped into my brain that maybe I could come up with something that could come over the radio.''

Modern soundproofing in cars and loud radios meant drivers were often unaware of an emergency vehicle until they had already caused a delay, Mr Wilkie said.

Cars within a 300 metre radius of the emergency vehicle will hear the message that plays every eight seconds for around 40 seconds.

Mobile phones, pagers or other devices would not be affected and it would not be turned on within 600 metres of hospitals, fire stations and police stations to limit inconvenience to nearby residents.

Mr Wilkie predicts a high demand for his invention with 20,000 emergency vehicles in Australia and 100,000 in the United States alone and he plans to make them all in Geelong.

Production is dependent on approval from the Federal Government and Australian Communications Authority as an exemption is needed for legislation that prevents people overriding radio transmissions.