Yes, however in you car analogy is that you can choose to go via the motorway or not.
Not if they didn't build you a motorway - it sucks trying to get into East Anglia for that reason, the only big road (the A14) is insanely overloaded. But, end of analogy I guess!
My solution would be for example say an upto 40Mb connection is £20 then if your exchange can only support upto 8Mb then you pay £4, upto 16Mb £8. Sounds fair to me and it might cause providers to upgrade the exchange.
Hasn't that sort of happened? As far as I can tell bog standard ADSL is now dirt cheap, whereas the high speed connectivity of Virgin Media, BT Infinity etc. commands a bit of a premium.
Don't forget as soon as the mobile operators stop focussing on charging silly money for haf a stinking gig of data on contracts lasting longer than those with the red horny guy, which should happen with a bit more competition, then we should have mobile data as an additional option.