A man and woman, believed to be in their 20s, returned to their car Thursday afternoon after a dog that was left sitting in the vehicle during a heat wave escaped and ran onto the busy Gardiner Expressway.

The trio did not speak to media, but picked up a note left on their dashboard by police before driving away.

Their arrival marked the end of an afternoon incident for Parker, a Mastiff-mix, who made a daring run through traffic along Toronto's downtown Gardiner Expressway before stopping to rest in the shade of a stopped vehicle.

The dog was spotted running along the Gardiner's eastbound lanes, near its Yonge Street offramp, at about 1 p.m., as vehicles slowed to pass the animal.

The dog's escape happened shortly after Toronto police were called to the Loblaw grocery store parking lot at Jarvis Street and Queens Quay, after they were alerted to a dog left inside a parked car that had B.C. licence plates.

"He was panting heavily," said police Const. Matt Buss. "He was agitated, the closer we got to the car, but once we managed to gain some trust with him, we opened the door and we got the leash on him."

The officers started to give the dog some water, but the animal pulled out of the leash and ran. The dog made its way up a ramp onto the Gardiner Expressway.

Toronto police said the dog was exhausted after being trapped inside the overheated parked car and it stopped to rest in the shadow of a van that had stopped on the Gardiner.

Animals left inside parked cars on hot days are at in danger of overheating, police have warned. A dog died after being left in a car parked outside the Vaughan Mills Mall earlier this month.

Toronto police said they have responded to 152 reports of dogs left in parked cars this week.

After waiting nearly three hours for the dog's owners to return to their parked car, the officers left a message, saying that the dog had been taken to Animal Services.

Animal Services reported the dog to be in good condition.

The owners are expected to face charges when they pick up their dog.

With files from CTV Toronto's John Musselman