Walking neighborhood/city streets off leash is a real liability.
walk Pongu off leash in the city; I've tested it at off hours (by which I mean going down side streets at 4 or 5 a.m. -- and even then, taxis come through my neighborhood every couple of minutes), and very occasionally by necessity when I find myself unexpectedly carrying large and unwieldy burdens and can't manage the leash.
He's pretty close to perfect. I can have him hold a competition Heel for several blocks if necessary, and I can also have him on a more relaxed 15-foot invisible emotional tether. The one and only good thing about a fearful dog is that he won't willingly stray from my side.
So I can
do it. But I still think it's an awful risk and I would never dream of doing it routinely. All it would take is one stray cat or one loud truck backfire (or a gunshot, we have those too here...) and a speeding taxi and bam, I wouldn't have a dog anymore.
If you're truly out in the country in the middle of nowhere, I guess you might not have to worry about this. But if you're anywhere
else, I wouldn't chance it. No matter how good your training is, it's not worth the risk. Dogs are dogs. They make mistakes, they get tempted to chase things, they get scared and bolt. It's up to us, as responsible owners, to prevent those momentary lapses from ending in disaster. A leash is an important way of doing that.