Please don’t smoke in vehicles.
I got motion sickness.
"How was the ride?" "Oh, it was terrifying! I spent the whole time trying not to pee my pants."
You know that 乗り has something to do with riding and that 物 is a thing. So what is a "riding thing?" Nowadays, at least, that would be a vehicle.
This word uses the kun'yomi readings for both kanji, but you know them both now, so you should be able to read this too!