GPS has an accuracy of a couple of meters (5m IIRC). DGPS has guaranteed decimeter accuracy and with really accurate localised DGPS you can get mm precision.
If this wasn't true, GPS wouldn't work for people walking about. And I can quite happily monitor myself with mobile Google Maps + GPS walking up and down my street in a non-straight line (so it's not just inferring where I'm going and jumping 100m that way). And that's a phone's built-in GPS with a crap aerial. When driving it knows what side of the road I'm on. My little chewing-gum-stick-sized GPS does this as well.
Speeding up traffic greatly reduces fuel consumption / litre over the normal crap speeds that are managed at rush hours. The fuel efficiency of some cars will peak at higher speeds / revs, and also if you're sat in traffic you're burning through fuel without going anywhere. Or stop-start driving, which is probably worse since you barely move but use lots more fuel...
Using the hard shoulder is such a sucky fucktarded idea that they should be sacked for thinking about it. What if someone crashes and needs help? What happens when we start filling THAT lane up- you'll be stuck with traffic that's just as bad but with no emergency lane.
I'd suggest that all MPs and council buildings have an artificial 2-hour lead time applied to their emergency service needs so that they can see what happens when an ambulance is stuck in traffic.
That £6Bn would be best invested in public transport. Or sorting out the abysmal state of our roads. Or bribing Her Majesty to legalise Gordon Brown's hanging. Hell, or bribing the government to legalise weed so we can all forget about this big brother crap....