Jackson said the trampoline was precariously held in place by two ropes and was bouncing forcefully up and down as the car moved.
"I couldn't believe it when I saw it... it was hanging over the side of the car. I've seen beds on [car] roofs but not that wide, nothing like this," Jackson told Stuff.co.nz.
He said the ropes, which were looped through the car's windows, were holding on "for dear life."
"[The driver] wasn't going slow, every time she sped off and then stopped it was bouncing up. And she wouldn't have been able to get out of her car because the doors were tied shut to hold it down," Jackson said. "Everyone was slowing down to check it out."
Tianna Maxwell, who was visiting the city and staying at a friend's apartment on Quay Street, captured video of the trampoline-carrying car passing on the road below with police in pursuit.
Maxwell told One News Now she was surprised to see the officers following the car, as she "would have thought the police would have pulled them over."
Police revealed the driver had actually already been pulled over prior to Maxwell's video and issued a fine. The police cars in the video were escorting the vehicle to its destination to ensure the drive ended safely.
"The vehicle in question was stopped on the city side of the Harbour Bridge and issued with an infringement notice for traveling with an insecure load," a police representative said. "Following this the police unit ushered the vehicle off the motorway and followed the vehicle a short distance to their final destination to ensure there was no further risk to the public."
