Then the wrong-way car slams into the oncoming car before crashing into the barrier and spinning across the road.
Senior Sergeant Anthony Bond told the Herald a 42-year-old woman had entered the motorway at Mosgiel before heading north while in the southbound lane.
He said a 79-year-old woman and an 80-year-old man were in the other car and noted that all three were lucky to survive, saying the time of the crash and the glancing blow struck meant the results were not worse.
“If it was a head-on, it would have probably resulted in a fatal, from any of the three occupants.”
Both cars were badly damaged but Bond said the elderly woman only suffered a minor knee injury and chest pain and the man was uninjured.
The alleged drink driver gave a breath alcohol level of 890mcg, more than three times over the legal limit, and declined medical treatment.
She was arrested and charged with drink driving and dangerous driving.
She also had her licence suspended for 28 days.