Invisible fences will not keep your dog safe.
This message brought to you by the elderly Labrador mix I picked up this morning.
The dog with two collars, one meant for an invisible fence plus another collar, but no tags.
The dog with a cataract in one eye, so I guess that would make it even harder for her to see hazards such as the cars on the nearby highway. Not that any dog is competent to navigate a highway.
She was sweet as pie, a well-cared-for pet, who immediately jumped in my car when I raised the back, sat quietly during the trip to my vet, and trotted into the clinic wagging her tail.
Is she chipped? Beats me; they’ll check when they’ve got time. Either way, this dog is probably heading for a stay at whatever facility animal control takes stray dogs. Hopefully her owners will find her. Someone plainly has cared for this dog, so I imagine they’ll be looking for her. Regardless, almost anything is better than her dying in agony with a crushed pelvis on the highway.
An invisible fence —
–won’t stop someone from coming onto your property and stealing or hurting your dog.
–won’t stop a stray dog from coming onto your property and killing your dog.
–most of all, if your dog goes through the fence for any reason, she will not be able to get back to your house because the fence will shock her if she tries to return. She may well get lost. She will quite possibly wind up miles from your home.
If you have an invisible fence and you are trusting that fence to keep your dog safe, you are primarily trusting to luck. If that luck runs out, your dog can very easily wind up in a terrible situation.
I will let my Leda sum this up, because her head tilt is so expressive.

Update: I hear the Lab mix I found this morning has been reclaimed by her owner. I hope after this, they take care to keep her safely off the roads and out of the woods and at home! And put a tag on her collar!