What does the maximum speed sign mean?

This sign stands beside a road you are driving on in heavy rain, with spray from other vehicles cutting your view. What does the number on it represent?

The highest speed allowed in good conditions, which these are not

A posted limit is a ceiling set for a clear, dry road with normal traffic. Rain, snow, fog and heavy traffic all put the safe speed below it, and driving at the number in poor conditions can still be driving too fast.

This sign is posted on the road you are driving and heavy rain has badly cut how far you can see. What speed does it allow?

No more than the number shown, and less than that when conditions call for it

A posted maximum is the highest speed allowed in good conditions, not a speed you are entitled to hold in any weather. In rain, fog, snow or heavy traffic the safe speed is lower, and driving too fast for the conditions is an offence even when you are under the posted number.

You pass this sign as you come into a built up stretch of road. From what point does the number on it apply?

From the sign itself, and it holds until another speed sign changes it

A speed sign takes effect where it stands, so you should already be at or below the number as you reach it rather than braking once you have passed it. It then applies to the whole of that road until the next speed sign, quiet stretches included. Slowing afterwards means you were over the limit on the part of the road the sign was there to protect.

The sign ahead carries the word MAXIMUM above a number. It is raining hard and the traffic around you is moving well below that number. What does the sign mean for you?

The number is the highest speed allowed in good conditions, so heavy rain means slower than that

MAXIMUM is exactly what the word says, a ceiling, and it is set for a road that is dry and clear with normal traffic. Rain lengthens the distance you need to stop and shortens what you can see, so the safe speed drops below the posted one. Driving at the limit in bad conditions can still be careless driving.

You pass this sign at the edge of a built-up area. How long does the number on it apply for?

Until another speed sign changes it, or the type of road changes

A posted limit runs from the sign until a new sign replaces it, which is why the sign just after a junction is worth looking for rather than guessing at. Where nothing is posted, the limit is the one the law sets for that kind of road.

You are travelling well below the number on this sign because the traffic ahead is heavy, and the driver behind you flashes their lights. What does the sign say about your speed?

The number is a maximum, not a speed you have to reach

A maximum sign sets a ceiling and never a target, so travelling below it because of traffic, weather or a heavy load is normal driving. Keep right where you can so faster traffic can get past, but do not raise your speed beyond what the conditions allow because somebody behind you is impatient.