Toll Roads and GPS

Alex writes in glowing terms about a German plan to use GPS to track trucks:

Some 800,000 trucks use Germany's 12,000 km of highways every day - all of these trucks will soon be tracked by GPS (i.e. from outer space!) and the big ones will be billed. The toll system will also be tied into traffic reports and routing systems.

As much as I would like to see the implementation of more toll roads to reduce congestion, I am not nearly so thrilled with the prospect of GPS tracking devices on vehicles. The reason? Shades of 1984.
I am willing to sacrifice some efficient congestion relief in exchange for more privacy.