At a T-junction your road ends and you must join another. Whatever direction you turn, traffic on the new road has priority. Your task is to slow down, look both ways, judge the gap, and pull out only when you will not force another driver to brake or swerve.
Crossroads work on similar principles but both roads carry equal priority. Turning right at a crossroads means waiting for oncoming traffic that is going straight or turning left. Do not rush this: impatience at crossroads is one of the fastest ways to earn a serious fault.
Box junctions are marked with yellow cross-hatching. You must not enter the marked area unless your exit is already clear. The one exception is turning right when oncoming traffic is the only thing preventing you from completing the turn: in that case you may wait inside the box.
At every junction, follow the MSM routine: mirrors first, then signal, then move only when safe. Watch for pedestrians and cyclists who may be crossing the road you are joining, especially near shops, schools, and bus stops.

