Ryan, your right about the 10% +2 but what the hell are you going on about with the lines!?
The lines as Pumpkin said are there to calculate your speed when the radar fails through the speed=distance x time formula, however, i have never seen these lines painted on the other side of the road to where the camara is. The camara takes a pretty panoramic shot so if you go onto the other side of the road it doesn't matter because the shot has still got you and the police use the radar speed but also they can still use the lines on the right side of the carriageway.
I'm confused by your post! But basically, there are very speed camara locations where lines are printed both sides of the road, the camara takes a wide angle shot and the rozzers can calculate your speed first by radar and second by the lines on the right side of the carriageway.