A single speed camera has raked in an astonishing £4m in fines in just three years.
The device, which was installed between junctions 19 and 20 on the M4 near Bristol in 2014, has snapped 40,320 drivers going over the speed limit.
Its haul of £4m makes it the biggest earning motorway camera in Britain.
In total, some 210,538 motorists have been caught since the cameras became used widespread in 2013.
Fixed penalties cost £100, meaning the total raised in fines currently stands at a staggering £21m.
Speed cameras on motorways often catch drivers out when variable speed limits are in place.
The M25 alone has eight of the busiest variable speed camera sites – with a total of 78,272 tickets raising £7.83m in fines.
The figures, released by price comparison website confused.com after a Freedom of Information request to UK police forces, show 6% of drivers have been caught by a variable speed cameras – with 78% claiming they did not realise the limit had even changed.
Amanda Stretton, from Confused.com, said: “There seems to be a perception among drivers that variable speed cameras are there to catch people out.”
The report concludes: “It’s likely the number of fines will rise further, with more variable speed zones planned across the UK as part of so-called ‘smart’ motorway schemes.”
Top pic: Rex