You are driving a car towing a caravan. On a single carriageway A-road you see a plain white circular sign with a single black diagonal stripe. A few miles later, joining a motorway, you see the same national speed limit sign again. Under Highway Code Rule 124, what maximum speeds does this sign actually permit for your car-and-caravan combination on these two road types?
- The sign always means 60 mph regardless of towing a caravan or trailer, on both the single carriageway and the motorway
- The sign always means 70 mph regardless of towing a caravan or trailer, on both the single carriageway and the motorway, the same as for a car not towing anything
- The sign means 50 mph on the single carriageway and 70 mph on the motorway, matching the limits for a car not towing anything
- The sign means 50 mph on the single carriageway and 60 mph on the motorway, both lower than the 60 mph and 70 mph limits that apply to a car not towing a caravan or trailer
Why D? And why not the others?
Correct answer: D. The sign means 50 mph on the single carriageway and 60 mph on the motorway, both lower than the 60 mph and 70 mph limits that apply to a car not towing a caravan or trailer
The national speed limit sign itself, the plain white circle with a black diagonal stripe, does not state a single number; it means that the ordinary statutory maximum for that class of vehicle on that particular type of road now applies, and Highway Code Rule 124's table sets that maximum differently depending on the vehicle. For a car or motorcycle not towing anything, the limit is 60 mph on a single carriageway and 70 mph on a motorway, but for a car towing a caravan or trailer, the table sets a lower maximum of 50 mph on a single carriageway and 60 mph on a motorway, because a towed load increases stopping distances and reduces stability at speed. That rules out reading the sign as always meaning a flat 60 mph or a flat 70 mph regardless of what is being towed, and it also rules out assuming the towing limit only reduces the motorway figure while leaving the single-carriageway figure the same as an untowed car's; both figures drop together for a towing combination, which is exactly why the same physical sign can permit a different speed depending on what is attached to the vehicle displaying it.
Source: Highway Code Rule 124, speed limits table (GOV.UK)