Which vehicles are allowed to move at this traffic signal?

Explanation

The yellow and red cars.

Look carefully at the light itself: an arrow pointing upwards is drawn on the main green lamp, the additional section on the right is also lit with a green arrow, but the additional section on the left has stayed dark. That is, only straight-ahead movement and a right turn are permitted at this junction, and any movement to the left — including a U-turn — is prohibited.

Now judge each vehicle by its intended movement. The yellow car is going straight without an indicator; the green upward arrow permits it. The red car has signalled right; the additional section on the right is lit, so it is permitted. The blue car has signalled left, and the tram rails also curve to the left at the junction; because the left additional section is dark, neither the blue car nor the tram has the right to move.

The key rule is this: when an arrow is drawn on the green lamp, the green is only for the directions shown, not for all directions; and an unlit additional section means movement in that direction is absolutely prohibited, not "conditional". Its safety reason is the left turn — the most dangerous junction manoeuvre, because it cuts across the oncoming traffic. By leaving the left section dark, the junction's designer has eliminated that conflict entirely. Common trap: imagining that a lit green lamp means every direction is free.

• Adding the tram is tempting because you imagine the tram is an exception; but the rails go left and the left additional section is dark, so the tram has no permission to move either. • "All vehicles" also includes the blue car with its left indicator; movement to the left is prohibited by this light, so this option is wrong from the outset.

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