Automatic Number Plate Recognition (ANPR) cameras have been used to monitor the average speed of traffic over sections of the road.
READ MORE: M4 named slowest motorway in the UK
The temporary speed limits are legally enforceable, meaning drivers who exceed this top speed are liable to penalties.
And people do get fined, as court filings show.
This newspaper has previously reported the names of the motorists who have been handed court fines for speeding on the M4 while Smart Motorway works were being carried out.
And in the past three months, more Berkshire drivers have been in court for the same offence.
David Gray, 53, from Newbury, was caught driving at 57mph on the M4 in Bray on November 5, 2020.
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He was fined £288 and ordered to pay £147 in court costs.
As well as this, Gray was handed three points on his licence.
He appeared at Wycombe Magistrates’ Court on November 23.
Ahunna Onyenso, 44, of Greenham Avenue, Reading, was caught going 68mph on the M4 at Waltham St Lawrence on September 26, 2020, breaking the temporary 50mph speed limit.
READ MORE: Man who broke M4 speed limit in court
He was fined £100 and made to pay £34 in a victim surcharge after appearing at Reading Magistrates’ Court on January 20.
Robin Richards, 60, of Monkey Island Lane, Bray, Maidenhead, was caught going 22mph over the temporary 50mph speed limit on the M4 in Bray on October 22, 2020.
He was fined £140 and made to pay £90 in court costs at Wycombe Magistrates’ Court on December 1, 2021.