The introduction of smart motorways has seen a big rise in speeding fines. According to data collated by the BBC's The One Show, between 2010 and 2015, fixed penalties issued on smart sections increased from 2,000 to a whopping 52,000.
There are more than 236 miles of smart motorways in England, which use the hard shoulder and variable speed limits to control traffic flow. The government says they are not there to generate revenue but are used to improve capacity.
Smart motorways are operated by Highways England, which uses overhead gantries to direct traffic into open lanes and change speed limits depending on the volume of traffic (the gantries also containing speed cameras).
A further 200 miles of smart motorways are currently under construction or in the planning phase.
The One Show asked 12 police forces in England which monitor major stretches of smart motorway, including parts of the M1, M25, M4, M42 and M6, for the total number of speeding tickets and fines collected.
The majority of forces responded, with half supplying directly comparable data, showing that a total 52,516 tickets had been issued on these stretches in 2014-15 compared to 2,023 in 2010-11.
That meant the revenue going to central government every year increased to more than £1.1m, from £150,600 five years ago.
There is just one stretch of smart motorway on the M9 in Scotland - this saw tickets increase from 9 to 41 over the 4 years. No data was supplied by police for the stretch of the M4 in South Wales.
On one section of the M1 in Nottinghamshire, police issued 8,489 tickets, amounting to £425,000 of fines, in 2015. In 2010, it issued no fines at all.
Nottinghamshire police defended the figures, saying the speed cameras had only been fully operational since 2013.
Nottingham-based motoring lawyer Paul Wright said he had seen a "deluge" of cases along one stretch of the M1.
He told the BBC: "A cynic might say that it's another way of getting more and more money out of the motorist, over and above what we're paying already.
"And it's an easy way to extract fines from people, because once you're clocked over the limit by the camera, it's very difficult to fight against that."
And the AA told The One Show "questions need to be answered about the money being recouped".
It has also raised safety concerns about drivers having to use emergency refuge areas when the hard shoulder is removed to operate as an extra lane.
AA president Edmund King said more emergency refuges were needed and they should be twice as long, adding: "Only a couple of weeks ago one of our members broke down on a smart motorway. There was a red 'X' up but they still got hit from behind."
With motorway traffic forecast to increase by up to 60% from 2010 rates by 2040, the government is pressing ahead with its £6bn investment in smart motorways.
A spokesman for the Department for Transport said: "Smart motorways smooth traffic flow and cut congestion for millions of motorists, with evidence from trials showing they are just as safe as regular motorways.
"Enforcement is a matter for the police and it is clear that speeding costs lives. However, we have been clear for a number of years that speed cameras should not be used to generate revenue."
Shaun Pidcock, head of Highways England's smart motorway network, said they were "the safest motorways on the network".
"We have 100% CCTV coverage and we have people watching over them, making sure they're safe, and we can get people in the traffic office to them far safer and quicker than we can do on normal motorways."
For a full report, watch The One Show on BBC One, at 19:00 GMT on Monday 7 November.