@Gary F, DAB won't replace FM in vehicles
Your idea to help vehicle reception by broadcasting the signal on two different frequencies is all very well, except for the minor detail that DAB already does something like that - the DAB signal is actually broadcast on (I think) 1536 different subcarriers, making it much more resilient to multipath interference (eg: signals bouncing off buildings as you drive by) than FM.
Of course, doesn't help hugely if the signal strength is weak to start with because it's too expensive to put up transmitters to fill the holes...
Biting the hand that feeds IT
