A camper van was filmed doing 70mph the wrong way along the busy A9, sparking calls for improvements to road signs and markings.
The incident happened just before 6pm on Sunday near Ballinluig in Perthshire.
Video of the incident shot by eyewitness Alan McConachie went viral on social media.
It is understood the driver became confused when the single track road turned into a dual carriageway.
Mr McConachie, 25, from Elgin, said: “I was behind the motorhome for a few miles.
“As the road became the dual carriageway, they swerved across the centre line into the fast lane of the opposing road.”
He said: “There were people flashing him. Drivers could see what was happening and moved lanes early.
“As I was passing, they were putting on their brakes, so I imagine they turned round.”
It is the latest in a series of incidents involving vehicles travelling on the wrong side of the A9 and campaigners said it lent weight to demands for an upgrade. Local Conservative MSP Murdo Fraser said: “This is a terrifying incident, which could easily have resulted in serious injury or death.
“In recent weeks we have had a spate of serious accidents on the A9, which again highlights what a dangerous road it is.”
Mr Fraser said: “Whilst there can never be an excuse for poor driver behaviour, the configuration of the A9 is undoubtedly a factor in the accident rate.
“The case for dualling the road is stronger than ever and I have been pressing the Scottish Government to advance the timetable for this vital work if that is at all practical.”
Independent Highland Perthshire councillor Xander McDade said: “This is obviously a concerning incident, but sadly not an isolated one.
“I can think of a number of recent occurrences where I have personally seen hire cars driving on the wrong side of the road.”
Mr McDade added: “There is a real need for increased signage to remind drivers to drive on the left, including with more on-road arrow markings when the road changes from single to dual carriageways.”
Local Conservative councillor John Duff said: “Thankfully no-one was injured, but I am sure it was a frightening experience for everyone who witnessed it.
“This highlights the need to complete the dualling of this section of major trunk road.” Police Scotland said officers had not yet been alerted to the incident.
A Transport Scotland spokesman said: “We are committed to dualling the A9 as soon as possible to improve safety on this important route.
“The £3 billion investment to dual the A9 between Perth and Inverness is one of the biggest transport infrastructure projects in Scotland’s history.
“Work is continuing across the route and road users are benefiting from the first section to be dualled between Kincraig and Dalraddy.
“Construction of the second section between Luncarty and pass of Birnam is underway and is planned to be completed in Spring 2021. We are also reviewing procurement options to bring forward the remainder of this programme.
“It is essential that we follow due process with the dualling programme which requires in depth planning and design to ensure that we deliver the right schemes at the right price as well as keeping impacts on communities, businesses and the environment to the absolute minimum.”