I fly airways in the USA with just nav radios.  Here in the US, they are almost all still associated with VORs.  

But in Europe and UK, there seem to be a lot of airways that are only flyable with RNAV equipped planes, because there are no VORs to use to guide you.  ( I'm not saying that there are no VORs in Europe, just that many airways do not have them where they would need to be to allow you to fly the airway with a set of nav radios.)