The operation of vehicles is prohibited if:

Explanation

Fitting yellow reflectors at the front of the vehicle.

The colour of reflectors is not a matter of taste but a shared language: white at the front, red at the rear, amber at the sides. At night, when his headlamps strike an unlit or stationary vehicle, another driver works out that vehicle's orientation from these colours alone.

Now imagine seeing a yellow reflection in the distance on an intercity road. Your brain reads it as "the side of a vehicle crossing the road", when in reality you are facing the front of a vehicle standing towards you. Those few seconds of misinterpretation consume your braking distance. That is why fitting yellow reflectors at the front prohibits operation independently of anything else. Memorise the rule in one short sentence: no colour other than white at the front and none other than red at the rear.

The question's trap is the tread depth option. The permitted residual tread height depends on the class of vehicle and is not a single figure for all; for a passenger car it is 1.6 mm and for goods vehicles it is lower. Before reading a figure as "low", you must see which class of vehicle the question is speaking about — that distinction alone changes the answer to several questions in this family.

• In the original wording this option concerns a goods vehicle, whose permitted tread limit is lower than a passenger car's (1 mm), so 1.4 mm is still above the limit and does not prohibit operation on its own; the same figure applied to a passenger car would give a different answer. • "In both cases" is correct when both conditions are defects; since the tread here is still within the permitted range, only one item remains.

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