I've read all the advice offered and it simply isn't good enough. My GO 5000, even when set to fastest route, often takes me off a perfectly good main road to land me in a dangerously narrow country lane with blind bends and no passing places, just to save (presumably) a few seconds. Yesterday, it sent me off the A31, up a mile or so of tiny country lane, then back on to the A31 a little further along! Recently, it did the same thing on the North Circular, routing me through a complicated 20 mph housing estate with huge speed bumps just to return me to the North Circular. No obvious time saving, but a difficult, uneconomic and anti-social addition to my route!
PLEASE do what has been suggested before and give us a button that instructs the device to use only motorways, A-roads and B-roads. I know that would rule out a lot of short cuts in built-up areas, but you could select the button for all non-town driving.