Many years ago I lived in a rural part of Florida on a 23 acre abandoned orange grove. I had a 10 ft. chain link fence with barbed wire around the top. On the gate a large red and white sign said "BAD DOGS- KEEP GATE CLOSED".
I worked for Animal Regulation and rescued Danes (and pit bulls that had hunting potential) I had 5 permanent residents, all Danes, and various fosters. 2 of the permanents had never been off a chain until they came to live with me- one was mellow and had joint issues, one was pretty neurotic. The best thing mentally and physically for those guys was to get out and run. Another of the 5 was a trained bodyguard.
I told the electric company guy more than once that if there were cars around the trailer to stay in his van and honk, that if the cars were there, someone was home, and if someone was home then the dogs might be loose. "Drive up and honk" is just simple farm etiquette anyway, as far as I'm concerned. When anyone else did it the dogs would come up to the house and mill around, wagging their tails to greet the visitor. I tried to explain that while normally reliable, if they'd been out running and getting "packed up" 5 dogs with a combined weight of about 850 lbs could be VERY dangerous.
Several times I heard his van pull in and his car door, and raced out to find him already halfway around the house. I'd warn him, and he'd shine me on.
One day I was taking a shower, and didn't hear him pull in. I heard the dogs going crazy, though. I threw a robe on and ran out, to see the man in his van, with the most terrified look on his paste white face I had ever seen. The dogs were trying to chew his windows out, I could hear their teeth clicking on the glass. Snarling, slobbering beasts with whale eyes surrounded him. I called them off one at a time and put them away, but kept the bodyguard dog at heel beside me. He slowly rolled down the window, and puked down the side of his van.
He said he had barely made it around to the side of the house when he saw all of them stand up out of the grass at the edge of the trees (about 7 acres away) He turned and ran, and barely made it to his van in time.
I really shudder to think what would have happened if he hadn't seen them until he was too far from the van.
After that, I put a double lock on the gate, and everyone called from the gas station up on the highway (this was before cell phones) before they came over.