The cars will drive through the intersection in the following order:

Explanation

Blue at the same time as green, then yellow.

The key to this question is a simple point often missed in the exam: "order of passage" does not always mean going one at a time. Two vehicles whose paths do not cross each other pass through the junction simultaneously, and neither has to wait for the other.

The blue and green cars are travelling on one road and their paths have no point of intersection; that is why they can enter the junction together. But the yellow car comes from the crossing road and its path cuts across both of theirs; it must stop until both have passed and is the last to leave the junction. Safety reason: a junction must be cleared in the shortest possible time. If drivers whose paths do not intersect also wait for one another, the queue behind the junction grows long and those standing at the back start making hasty manoeuvres. By contrast, a vehicle that cuts across others' paths must wait until the last moment, because its error leads directly to a front-to-side collision.

Worth memorising: before arranging the order, picture each vehicle's path on the image and see which lines cross each other. If two paths do not intersect, those two are simultaneous and you should look for exactly that case among the options; an option that lines everyone up in single file is usually the trap of the question.

• This option assumes all three cars must go one at a time in turn, and it also puts the yellow car first; whereas yellow cuts across the paths of the other two and must go last.

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