The introduction of tougher punishments for the most serious speeding offences has been welcomed by motoring groups.
Drivers caught at speeds excessively above legal limits face higher penalties in England and Wales from Monday.
AA president Edmund King described the changes as “an effective way to penalise offenders”, the Press Association reported.
The Sentencing Council said the move aims to ensure there is a “clear increase in fine level as the seriousness of offending increases”.
It follows responses to a consultation arguing previous guidelines did not properly take into account the increase in potential harm that can result as speed above the limit rises.
Some 244 people were killed in crashes that occurred when a driver was breaking the speed limit on Britain’s roads in 2015.
King said there is “no sensible reason” for excessive speeding, adding: “It is only right that these extreme offenders are punished severely.”
He went on: “Responsible drivers will welcome the changes coming into force today.
“The majority of drivers who keep to the correct speed, as well as driving to the conditions, won’t be affected. It is only those who deliberately drive dangerously who will end up in court.”
What speed do I have to be going to be penalised under the new rules?
If you’re caught doing 51mph in a 30mph zone or 101mph on a motorway, the new rules will apply to you.
How is the penalty changing?
Under new guidelines for magistrates, fines will start from 150% of your weekly income, rather than the previous level of 100% if you’re caught above those speeds.
What is the maximum fine?
The maximum fines allowed by law remain the same, so speeding drivers cannot be fined more than £1,000 unless the offence takes place on a motorway, where the limit is £2,500.
RAC Foundation director Steve Gooding said while the new measures “underline how seriously the courts take speeding offences”, the limit on fines means there is not a “level playing field”.
He also questioned whether police officers have enough resources to ensure the tougher punishments have an impact on road safety.
The number of full-time dedicated roads policing officers in England and Wales (excluding London) fell by 27% between 2010 and 2015.
Gooding said: “While we broadly support linking the amount of the penalty with income, the cap on the level of fines means that this link is broken for high-income drivers - hardly a level playing field.
“For speeding penalties to be effective three things have to be true: they have to be severe enough to hurt, motorists need to know what they are and believe there is a realistic prospect of being caught if they go too fast.
“We worry that other pressures on police time will seriously undermine the effectiveness of this stiffening of sanctions.”
Gary Rae, campaigns director for road safety charity Brake, said: “Toughening the fines and penalties for speeding is long overdue.
“I hope that magistrates ensure the new sentences are consistently applied.”