Are your neighbors shoving the dog out in the morning to take care of business while they get ready for work? If so, they need to get up early and go out with the dog. The poor thing is ready to socialize a bit in the morning.
We have a dog and it drives me crazy to think of leaving him out to just bark and bark. Some owners don’t seem to mind though! Our neighbor on one side has two barking dogs and they go insane sometimes late at night. Why are they out so late? Another neighbor leaves her dog out for hours but at least he has a low pitched bark. My dog and that one will bark at each other when they’re both inside, but not when they’re outside. Go figure.
@romanigypsyeyes - we found that leaving the radio on low, on a talk station, helped keep our dog calm while we were out.
Here’s another one for you guys. We just got some new neighbors, who seem very nice. They have a small dog. First day they moved in, we were driving away, and saw the dog in the middle of the road. My husband got out, and approached it slowly. The dog seemed very unfriendly, and my husband decided to stay away. However, he stood out in the middle of the road with that dog, because people can drive quickly, and could run into that little dog without ever seeing it.
I went down to the house to tell the owners, and the man was very unconcerned. He eventually sent his little kids up there to get it. It was kind of odd, because if I knew one of my little doggies was loose in the middle of the road, I’d be making a world record sprint to get that girl to safety.
So now we think, what do we do? They are casual with their dog, even in a somewhat busy road. So I guess if I see the dog out again, we knock on the door. But if they’re not around, I don’t think I’m putting an unfriendly dog in my car.
http://komonews.com/news/local/seattle-family-may-lose-house-over-barking-dog-11-21-2015
If your neighbor sues you because the dog barks… show up in court. 
I text the guy in the apartment next door when his dog barks non-stop. To be fair, when it was a new puppy, he left a note in his door saying to call or text him if she is barking too much. I’ve only contacted him a few times (once when I could hear his dog and cat fighting, didn’t sound like the cat was going to make it out alive! But it was fine…). You could suggest that maybe they aren’t aware that the dog is barking sometimes, and offer to let them know. 
It is not just early morning or late night barking that is a problem. I can hear the neighbor’s dog barking when I am in my home with the doors and windows closed. I sometimes work from home, and trying to conduct a conference call while listening to a barking dog is difficult. Our ordinance does not reference a time of day, just continuous or repeated barking that crosses property lines. Just because you don’t mind listening to your dog bark doesn’t mean the neighbors feel the same. Please be considerate.
Our last dog was a serious barker, we called her the doggie alarm system. At night, if we heard a noise and she didn’t bark, DH would roll over and go back to sleep. But no neighbors were harmed.
I’m not crazy about people who leave a dog outside, untended. Especially when they leave. Too much can happen. Agree the first step really is to speak with them. If they’re leaving it out while they get ready, maybe nicely offer suggestions. Like: give the pup a few minutes to do her business and bring her back in. Duh.
Btw, our new dog is also a barker, but a rescue that was found, adopted, given back, adopted and given back again. She’s a keeper, a sweetheart, sitting quietly at my feet right now, outside. A few minutes ago, she was barking at a squirrel, we quieted her. She needs time to feel secure. We work with her on that.
My dogs are barky little bundles…it’s in their design, just as much as herding is. I am very mindful of disturbing our neighbors. I can’t stop them barking entirely , but I can control the times so it won’t wake people up in the mornings or at night when people would be sleeping.
FWIW, it doesn’t matter if my neighbor on the other side of our fence makes friends with them…they will alert us regardless.
I would let the neighbor know that it wakes you up before it becomes a resentment issue. There is also a product called " Pet Corrector " It is a can of compressed air that makes a hissing sound. It will stop a dog from unwanted behavior. Maybe suggest it ( or buy it ) for your neighbor
Amazon sells it
@greenwitch that’s similar to what worked for us. We leave the tv on for her and she’s no longer crated when we leave. Being able to look out the window and watch tv seems to have virtually eliminated her separation anxiety 
@busdriver11 my neighbor is like that. They don’t have a fence and have an “electronic fence” that doesn’t work (or at least is ineffective). The dog is constantly in our front yard, driving my dog crazy, and in the street. Our road is a dirt road so people go slowly but we’re only a few houses away from a main road where people speed. I don’t like the dog but it’s because the owner’s an idiot and never trained her. I’m terrified that I’m going to come home one day and see the dog as road kill.
Plus my window in my room faces their house so all day I hear them screaming for her to come inside. Ugh!
I don’t like the manipulative nature of the “pretend to make friends first with the dog” advice. Who cares about being friends with the dog? That won’t stop the barking.
Tell the neighbor this dog has awakened you every single morning and could he step outside with the dog so it doesn’t disturb others? Could he walk it? Could he solve this problem?
Just today I saw a couple retrieving their golden retriever, a very large pup, off the freeway offramp! Yikes. The dog looked bigger than either of his humans, and was not trained - at all! It was playing with a toy in the middle of morning traffic, leash dragging behind it. A moving van and a bunch of cars stopped thankfully so the dog was not in danger, but it was obvious that the pup was a bit too much for the owners to handle. At that age, a dog should be already trained to understand some basic commands. Sigh.
I live in a neighborhood where most people have dogs. I have two of my own. We have a new neighbor with a dog who comes out of his house and howls every time he sees anyone in our yard. He has a dog door. You are all making me feel very fortunate, because the dog’s person is very concerned that he not be a problem. We are gradually working the problem–my dogs will now stop quickly instead of fence-fighting, and the neighbor’s dog now has a vastly improved recall as well. It wouldn’t have happened if we hadn’t talked about solutions.
All that said, we all try not to let the dogs out in that part of either yard in the very early morning.
@TranquilMind Regarding making friends with the dog. I did not mean pretend. I meant make friends with the dog. A dog is much more likely to stop barking quicker if he realizes you are not the enemy. All dogs are different but most dogs will not be nervous and bark if they know you are not a threat or a stranger.
I have no interest in manipulating anybody. Just being friendly so you can address problems when they occur.
My dog is not allowed to bark. He has taught himself to grab one of his large pony balls and barks with it in his mouth. We call it his “bark suppressor” .it actually works. He is a smart dog.
My dogs would gladly friend anyone , but that wouldn’t mean they still wouldn’t bark at them.
They are corgis and they generally bark to alert us of anything they perceive as a threat. They are known to be barkers. They bark when anyone opens the gate, including us.
The only neighbor who would actually be bothered by them is a night owl and he told me that they don’t interfere with his sleep or bother him. They are not outside for longer than a potty break without us.
We can hear the neighbor’s dogs on the other side of our house.One of them yelps like it is being kicked in the head , pretty much on a daily basis , but neither of them disturb us.