In the case of this sign, the effect of the sign used with it relates to

Explanation

Passenger cars, and also lorries whose permissible maximum mass is up to 3.5 tonnes.

What you see in the picture is not a main sign; it is the "type of vehicle" supplementary plate — a white rectangle with a side view of a passenger car. The job of this plate is to limit the scope of the main sign to a defined class of vehicle. Under the rules, a supplementary plate bearing a car symbol applies the effect of the main sign to passenger cars and also to lorries whose permissible maximum mass does not exceed 3.5 tonnes.

The practical consequence is this: a three-tonne delivery van within the zone of that sign behaves like a passenger car and is subject to the same restriction, whereas a seven-tonne lorry is not addressed by that sign at all. So this plate simultaneously brings one group in and leaves another out.

The figure of 3.5 tonnes was not chosen at random and is the principal boundary throughout the traffic rules: the boundary of category "B" licences, the boundary of many speed limits and parking rules. Its logic is technical too; vehicles lighter than this limit are, in braking distance, dimensions, turning radius and behaviour in curves, much like a passenger car, but above it the vehicle enters heavy-vehicle behaviour in all these respects.

Worth memorising: the car symbol on a supplementary plate takes in passenger cars "plus" light goods vehicles. The exam trap is the option that confines it to passenger cars alone, or that attaches motorcycles — which have their own symbol and their own separate plate — to it.

• Confining the sign to passenger cars is half its meaning; lorries up to 3.5 tonnes are covered too, and that point is the very subject of the question. • A motorcycle has its own separate symbol and supplementary plate and is not covered by the passenger car symbol.

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