Really, when it comes to car navigation, what do you need? An up-to-date map, so you know which roads are currently available to you; live traffic information, so you can avoid the queues, crash sites and roadworks; and, of course (knowing me), it should be free or at least as cheap as possible.
Taking the quickest route while driving is like a photon following Fermat’s principle.
To be honest, in light of these requirements I don’t think good ol’ paper maps are an all that great of an option nowadays. Paper maps cannot easily be updated and certainly don’t show live traffic information. While it’s true that the radio provides traffic information, it can be inconvenient to have to personally interpret such reports when driving in unfamiliar territory or when in a hurry. But then, a map doesn’t cost battery and the radio doesn’t cost mobile data fees. One digital alternative is satnav built into the car itself. However, this can get expensive and, moreover, is not updated very frequently, if at all.
It seems then that the cheapest and most useful way of navigating is by a satnav app installed on your smartphone. If you still don’t have a smartphone, that’s one reason to embrace the future and get one. (Along with a solid phone holder.) One of my old favourite satnav apps, because it was entirely free, is Navmii. Its unique selling point was that it offered completely offline navigation. Hence, no data fees. (I was not interested in live traffic at the time.) Road maps of entire countries were downloaded onto your phone, and off you went. It got me around fine, travelling internationally without paying for mobile data.
However, when it comes to national travel (I.e. without roaming charges) the undisputed top app is Google Maps. It has great ratings and appears to be accurate in its live traffic, which it says it bases off anonymous mobile phone data. The data usage of the app is minimal; it doesn’t drain my 250 MB/month data allowance anyway, which is the cheapest SIM deal around. Granted, you need a data plan of at least a few pounds a month, but this can be used for looking up other useful information on the go. And for the time savings gained, I think that’s worth a few pounds a month.