The thought is that "subway" mass transit can be full of people, even stuffed, but "commuter" lines are a bit lighter after they deboard passengers at the first few suburbs and you can find a nice comfy seat somewhere around the midway point.

Commuter lines can be pretty rough. I've been on some gnarly NJ Transit trains heading out of NYC.

The midway point of this line is Palo Alto, which is also a big destination. There are several other stations in the middle which are also big destinations.

Here in Southern Ontario (GO train) I have never seen aisles full with passengers. Although on the lower level there are some people standing, the upper deck is usually all seated. Often with some free seats.

Right, because everyone is too busy driving their cars, clogging up your poorly designed expressways. 401 traffic is hell at any hour of the day.

The GO Train is probably my favorite commuter rail service. People line up properly at the doors, it's never too crowded, it's clean, there aren't delays very often, and it's generally civilized.

Iunno, on rush hours' Lakeshore West trains going into Union, if you're not on by Bronte, you ain't getting a seat.

Regarding exhaust fumes, get a seat at the back of the train: https://www.thestar.com/news/gta/2017/02/07/go-transit-passe...