Ministers today announced their intention to bring in drug-drive limits in Scotland, days after the Scottish Conservatives called for action.
The move by justice secretary Michael Matheson also comes three years after ministers put it off when the UK Government announced limits.
Limits on the amount of specific drugs drivers can legally have in their bloodstream will follow - as are in force south of the Border.
They will be enforced with new "drugalyser" testing devices and are expected to be introduced in 2019.
The Scottish Government said new tests to detect these levels should make it easier to convict offenders as police will no longer have to prove a motorist was driving in an impaired manner.
Officers currently have to reply on roadside tests, such as for co-ordination and balance, or physical cues such as pupil dilation, followed by a urine test at a police station.
However, penalties, which are controlled by Westminster, will be unchanged - a minimum 12-month driving ban, up to 6 months in prison and a fine of up to a £5,000.
Mr Matheson's announcement comes four days after the Scottish Government responded to the Conservatives call for action by saying it was "considering very carefully whether evidence shows that specific drug driving limits should be introduced in Scotland.”
Two days later, the general election was called.
Mr Matheson said today: "While it is a long-standing offence to drive while impaired by drugs, by introducing new drug-driving limits and roadside testing for the presence of drugs, we will strengthen the ability of our police and prosecutors to tackle the minority of drivers who recklessly put other road-users and themselves at risk.
“Under the new offence, evidence of impaired driving will not be required, with our law enforcement agencies instead able to investigate and prosecute on the basis of a driver being above the specified limits for individual drug types.
The minister said discussions were continuing with Police Scotland, the Scottish Police Authority, and the Crown Office and Procurator Fiscal Service on the operational requirements, including roadside testing.
The necessary regulations, which will have to be approved by MSPs, will be published by the end of the year.
The individual drug limits will be issued "in due course".
Drug-driving was a factor in 65 crashes in 2015, which caused six deaths, according to the latest Scottish Government figures.
In 2014, when limits for 16 recreational and prescription drugs such as cannabis and cocaine were announced for England and Wales, Scottish ministers said they would “monitor developments”.
The limits were introduced in 2015.
Scottish ministers have had the power to do the same since 2013, but Mr Matheson said they had decided to focus first on lowering the drink-drive limit, which was introduced at the end of 2014.
Neil Greig of motoring group IAM RoadSmart, which has campaigned for drug-driving limits in Scotland, said: "It is great news for road safety that Scotland has finally decided to catch up with the rest of the UK and introduce limits for drug driving.
"These limits, plus roadside testing, have led to thousands of impaired drivers being prosecuted swiftly south of the border."
The introduction of drug-drive limits was among a number of recommendations by Sir Peter North in a report seven years ago that had been commissioned by the UK Government.
Sir Peter said: “I was very pleased to hear of the decision of the Scottish Government to proceed with reform of the law and practice relating to the offence of driving under the influence of drugs, following on from the recommendations that I made.
I believe that such reforms, when combined with the well-regarded decision to lower the drink drive limit, will make a major contribution to road safety in Scotland.”
Chief Superintendent Andy Edmonston, head of road policing for Police Scotland, who welcomed the move, said: "I would also remind motorists that it is currently illegal to drive whilst unfit through drugs and that remains a focus for us.”
On Monday, Scottish Conservatives justice spokesman Douglas Ross said: “The evidence is clear - drug driving is just as dangerous as drink driving. Yet in Scotland, the government has simply failed to respond to this menace on our roads.
“We need immediate action now to bring a halt to the growing number of deaths and injuries caused by people on drugs getting behind the wheel.
Mr Ross said Scottish research by Forensic Science International showed driving under the influence of cannabis and drink-driving led to the same number of deaths between 2012 and 2015 - one in five of the 118 cases covered.
He said today following Mr Matheson's announcement: “This is welcome news and comes after sustained pressure from the Scottish Conservatives for action.
“Under the SNP, Scotland was lagging behind other parts of the UK and the menace of drug-driving was going unpunished.
“We will keep the pressure on the SNP to ensure that these reforms are introduced speedily so that everyone on our roads is safer.”
Scottish Liberal Democrat justice spokesman Liam McArthur said: “I welcome this step to make drug-driving enforcement more effective.
"Ensuring there are no loopholes in the legislation will make our roads safer and save lives."