The operation of vehicles is prohibited if:

Explanation

Fitting tyres with different tread patterns on the same axle.

The two tyres on one axle must be twins. If the tread pattern differs left and right, the grip coefficient on the two sides is not the same, and that difference shows itself the moment you brake hard or on a wet surface: one wheel locks or slides sooner, the braking force becomes asymmetric, and the vehicle rotates about its own axis. On wet asphalt, the tread that clears water better keeps its footing while the other side slides on the water film; that is, the vehicle becomes half-controlled in an instant.

The same logic applies to combining new and worn tyres, studded and summer tyres, and different sizes on one axle. Memorise the rule not as a dry prohibition but as a physical principle: left–right symmetry is a condition of stability.

Now look carefully at the figure in the second option. For a passenger car, the permitted residual tread height is 1.6 mm and the prohibition begins below that figure. A tyre with exactly 1.6 mm of tread is still on the legal boundary, not beyond it; so this condition does not prohibit operation on its own.

That is the exam's trap: a figure sitting on the boundary looks "low" and pulls the candidate towards "in both cases". Memorise the figure together with its boundary, not by a feeling of more or less.

• 1.6 mm is exactly the permitted limit for a passenger car, not below it; the prohibition begins when the tread falls below this figure. • Since the second condition is still within the permitted range, "in both cases" becomes wrong and only the difference in tread pattern on one axle remains.

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