Road Markings and Traffic Control
Lines down the middle
A broken white centre line may be crossed to overtake or turn when it is safe. A solid white line on your side must not be crossed except to pass a stationary obstruction or to enter a side road. Double solid white lines mean neither side may cross. Where a solid line runs alongside a broken one, the rule applies to whoever has the solid line nearest them.
Lines at the edge and at junctions
Yellow lines along the kerb control parking and waiting; the more lines and the more yellow, the stricter the restriction. At junctions you will meet a solid white stop line (with STOP) or a double broken give-way line. Stop behind the line, never on it.
Box junctions, crossings and lanes
A yellow box junction must not be entered unless your exit is clear; the exception is waiting to turn right, blocked only by oncoming traffic. Zebra crossings are marked by broad black-and-white stripes with zig-zag or hatched approaches where overtaking is banned. Hatched areas bordered by solid lines are off-limits; those with broken borders may be entered only if necessary and safe. Lane arrows commit you to a direction once you are in the lane.
Traps: confusing a give-way line with a stop line, and forgetting the box-junction exception for a right turn.
Rule of thumb: if the line nearest you is solid, treat it as a wall; if it is broken, treat it as a dotted hint that crossing is allowed when clear.