Drivers who kill could receive life sentences as part of new reforms this week.
The sentences can be handed to dangerous drivers who kill and careless drivers who kill while under the influence of alcohol or drugs from Tuesday.
Each crime currently holds a maximum prison sentence of 14 years.
The changes have been made as part of the Police, Crime, Sentencing and Courts Act.
The new legislation – which was first muted in 2017 – will also create tougher sentences for those who cause serious injury by careless driving.
The increase will apply to offences in England, Scotland and Wales, but not Northern Ireland, which has separate road safety laws.
Steve Gooding, director of the RAC Foundation, said: “Drivers exhibiting the worst behaviour on the roads are a danger to us all.
“Those who behave with disregard to the risk they pose deserve the stiffest penalties when their actions rob others of their lives.
“Involuntary manslaughter already carries a maximum penalty of up to life imprisonment so it is hard to argue that killing someone with a car doesn’t warrant a possible sanction of similar severity.”
The government said the Crown Prosecution Service will still charge people with murder or manslaughter where there is evidence that a vehicle was used as a weapon to kill or commit grievous bodily harm.