Witnesses said both drivers, one male and one female, were elderly and refused to yield to the other because they felt they had been the first to drive onto the bridge.
The two remained in the stand-off for at least 30 minutes, causing major traffic backups in both directions.
Police cited both drivers for obstructing traffic, which carries a fine of about $190.
"I assumed someone had an accident or jumped off the bridge or something like that, so I hopped out of the car," Valenzi told DailyTelegraph.com.au.
"I had never seen anything like this in my life. I spoke to both motorists and they both refused to move because they both believed they had entered the bridge first and had right of way," he said. "The traffic was banked up to both main roads with every third car turning around."
