kEiThZ
Superstar
I stumbled across some evidence to back this up. According to Wikipedia, Brightline's "Select" coaches (their name for business class) have "21-inch (530 mm)-wide seats" while their "Smart" fare coaches (economy) have "narrower 19-inch (480 mm)-wide seats." Now there is no guarantee that VIA will use the same seats as Brightline, but there is a good chance they will since they are going for the same 2x1 seating arrangement in business class.
Will add that this is way more comfortable than bus or plane. A 20 -21" wide seat is what you get on domestic business class. And a 17-18" wide seat is what you get in economy. The CSeries/A220 has 18" wide seats with one 19" wide seat or airlines can opt for 18.6" wide seats across the whole row. That's the closest you'll come in the air to what VIA is probably likely to offer with the new fleet. Never have to worry about armrest wars on the train.




