What I haven't seen here is any mention of any kind of life cycle analysis of any transportation options.
I drive a 15-year old small Toyota Highlander with about 205,000 miles on it. We live about 30 miles from town on a dirt road, often rutted and marginally passable during monsoon season. We batch our trips to town, usually doing our errands when we have medical appointments. Think Little House on the Prairie.
I have never lived anywhere that I didn't need a car to get around. Even in Nuremberg I worked in 3 different locations and had meetings in a 4th. Public transportation was not adequate to get to any of them.
At 73 I've purchased a total of 5 cars. I've bought new or nearly new cars and driven them till they dropped. That's usually around 175,000 to 200,000 miles.
A few years back I was considering getting a hybrid car. Then I read an article similar to what I'm posting below. The basic premise is that just because something, in this case a car, is touted as environmentally friendly, it doesn't mean that its cradle to grave environmental costs aren't significant.
Lots of assumptions are made, but without a thorough comparative analysis it's impossible to know what kind transportation or any other product is the better choice for the environment.
Beyond that, as of today, I see no point in guilting myself or anyone else for flying or driving or taking a train or a bus or a subway or a cruise on a big ship. Or for doing anything else that may be the only way we can do some things, even if that way doesn't appear to be the perfect one for the environment.
Now, here's the article: Should You Keep Your Used Car or Buy a Brand New Hybrid Car? It's pretty long, so I hope you can make it to the end.
If you do get to the end you will see how many factors go into a life cycle assessment. These and other factors go into determining the life cycle impacts of any kind of vehicle or mode of transportation.