The vehicle that I overtook was doing 30 mph.
Why is the car in front doing 30mph?
Not enough video is shown to prove it, but from the short bit that is shown I'd say the speed limit is 30mph!!
It's not automatic NSL (national speed limit) because it's a dual carriageway. The street lights present make it 30mph unless otherwise indicated. In the piece of film shown there are no speed limit signs, that I can see, (and repeater signs would not be necessary in the circumstances) however they may have been present earlier, (at the start of the dual carriageway) in which case the street lights will not be an indicator of the speed limit.
Just my observations from the film.
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www.speedlimit.org.uk/speed_markings.htmlThis is a brief guide to the law and practice of speed limit signs and markings in the UK
Any road with regular street lighting has a default speed limit of 30 mph unless signs indicate otherwise. The entry to a 30 mph zone must be marked by a "30" sign on both sides of the road, but no repeater signs are permitted within the zone (on the grounds that they might be confusing if some roads had them and others didn't). "30" roundels on the road surface are however permitted, with a special dispensation.
In some circumstances, where a side road has a lower limit than the main road, only one speed limit sign for the lower limit is needed, on the left-hand side of the road, and no signs at all are needed for the higher limit if there are repeater signs on the main road indicating the limit within 100 yards of the junction.
Where there is no street lighting, the default limit is 60 mph for single-carriageway and 70 mph for dual carriageway roads. This is referred to as the "National Speed Limit" (NSL), and entry to these zones is marked by the familiar "derestriction" sign with a diagonal black stripe on a white background. Repeater signs are not normally used but are not specifically prohibited.
Any other limit requires roadside repeater signs at regular intervals prescribed by law. The mere fact that a road runs through an urban or rural area makes no difference to the speed limit - it is the presence or absence of street lighting. Thus a lit dual carriageway in a rural environment would have a 30 limit unless signs indicate otherwise, and the speed limit through the snooty Cheshire village of Prestbury, which still refuses to have street lighting, would be 60 in the absence of 30 signs and repeaters.