She saw a car stopped in the middle of the road, and a man lying on the road beside a motorbike.
The man had lost consciousness, and one of the witnesses started performing CPR.
"We tried for quite a while, others were trying to direct traffic, to keep that flowing and stop people from stopping."
There was quite a bit of damage to the motorcycle, she said.
The woman who was driving the car involved was "really shaken up".
"She was in shock and in tears; didn't know really what was going on."
Fire crews arrived at the scene and tried to revive the motorcyclist, before St John ambulance staff arrived and tried to do the same.
But they were unsuccessful, Miss Cairns said.
Police said the Serious Crash Unit was investigating.