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Loud music playing on a car radio can prevent drivers hearing the sirens of
emergency vehicles. But Spanish inventors Javier Tester and Javier Cabrera have
a neat answer (WO 01/45066). Ambulances and fire engines, they suggest, should
send out a continuous radio signal at such low power that only cars in the
immediate vicinity can pick it up; this could be the same signal that turns
traffic lights green for them. Car radios that pick up the signals would
automatically mute the music. This would alert the driver to the presence of an
emergency vehicle, and allow them to hear the siren so they can get out of its
way.