The SPCA is warning dog owners to think carefully about car restraints after crash tests revealed only one harness on sale in New Zealand would protect pooches in even a low-speed crash.
Researchers for State Insurance tested 25 popular dog harnesses at the insurer's research centre in Sydney.
The impact tests found all but two of the harnesses failed to adequately restrain life-sized, correctly weighted dog dummies in simulated impacts, even at speeds as low as 35km/h.
Tests were conducted by dropping weighted harnesses at speeds of up to 35km/h. In-car testing was conducted using a specially modified crash test car at speeds of up to 20km/h.
Of the two dog harnesses that passed the tests, only one - the Sleepypod Clickit Utility - is sold in New Zealand. However, it is only available for pre-order due to high demand, with a new shipment not due until next month.
The only other harness that passed - the Purina Roadie - is sold in Australia but not here.
SPCA Auckland executive director Bob Kerridge said dog owners should think carefully about using a restraint in their car. Some did not work effectively, while using them could be difficult because dogs generally did not accept them.
Mr Kerridge also raised safety concerns with ill-fitted harnesses.
"If the harness is not fixed correctly and there is an accident ... the dog might slip half-way out of a harness and it could throttle itself, so there are dangers," he said.
"The message is certainly, if you are thinking of a harness, firstly be very, very careful which one you choose in terms of the safety factor. Do they work and have they been properly tested? But secondly, will your dog take to it kindly?"
Mr Kerridge said dogs could be separated from passengers in station wagons using car boot dividers. Some came with a harness that kept dogs in a safe position.
"That's a pretty good idea actually because it allows them to be relatively free, but at the same time they can't go anywhere in the event of an accident."
State Insurance research manager Robert McDonald said the tests proved how an unsecured pet, travelling on the back seat of a car, could hit the dashboard with enough force to cause serious injury to the animal, even at a low speeds.
Mr McDonald said dog harnesses were critical because they restrained animals and avoided drivers becoming distracted by animals moving around inside the vehicle.
In a collision, unrestrained pets also had the potential to injure passengers in the vehicle.
"However our testing has unfortunately shown that most harnesses, while effective at restraining pets, are not safety devices and do little to prevent injury in a common low speed crash."