Completely agree. I love dogs but am quite allergic and imho transport infrastructure should prioritise the comfort/needs of people over their pets.

I wish the airlines would do differentiated flights (maybe adult-only or 12+ only for one flight a day on otherwise high volume route, and maybe an explicitly pet-friendly flight on a route, etc.). I live on an island, and especially now that most airlines (covid scheduling issues) have eliminated animals as checked baggage, anyone with an animal which doesn't conform to normal cabin transport is kind of screwed -- they have to use a specialty transport company, which either flies on dedicated cargo flights or something else, or they charter a plane ($5k minimum for San Juan to Miami).

My personal preference would be zero children, zero dogs, only well behaved cats, but I realize that's a niche flight preference, but on a route with hundreds of flights a week, one flight a week (or even one a month) should be easy to fill.

The bigger problem: people being allergic to dogs is quite common (above 10% of the population, I believe). I’m a dog lover and have 2 pooches that are my life, yet I am always baffled by people that feel they need to make everyone else deal with the pet they love.

99% of the time the problem is the owner in my experience. I don't like dogs near me, but I've rarely felt like the dog was the problem, it's selfish people who don't keep their dog properly leashed, close to them, and away from other people. Dogs shouldn't be on public transportation primarily because enough dog owners have shown they are unable to respect other people.

For me the problem is dogs’ unpredictability. I have a small dog, and although I believe 100% that she would never hurt a person or another animal, I still have her on a taut lead ready to yank her away when a stranger’s child wants to say hello on our walks, just in case.

I would want everyone bringing a dog on a train to be in that same level of control, and judging by the people and dogs I see out walking that’s an unreasonable wish.

I live in Japan now, and for the dogs I see in the city, the vast majority would easily pass this test.

However, from what I saw in America during the pandemic and before, the vast majority of American dogs would not.

That said, the bigger problems I see here are 1) how to deal with the bathroom problems (train trips last hours, and dogs don't hold it in very well), and 2) how to deal with peoples' allergies, and 3) how to deal with people just not wanting to ride near other peoples' animals. I think it's an insurmountable problem really, unless there's SO much demand that they can dedicate a whole train car to being pet-friendly (not likely). We already have ways of moving pets around: taxis and cars. Inside a city, just use a taxi. If you need to travel between cities, just rent a car. Yes, it's a lot of money, but if you can't afford that, then you can't afford a dog. Or just leave the dog at home. (If it's a cat, the cat doesn't want to take a trip with you anywhere.)

(edit) Finally, I just did a little research, and this isn't really a problem at all. You can already bring dogs and cats on trains here, both the intercity Shinkansen and the local trains. The catch is that it needs to be a small dog (or cat), and inside a carrier, weighing a total of 10kg or less. It looks like there's a small fee (less than $5) for the Shinkansen. So I don't see why any of this is necessary; it's a solved problem.