How common is it to trade those off against each other? "Oh, because I went to that conference, I'm cancelling all my driving meetings for the rest of the year." is a sentence that has probably never been uttered before I just did now.
I’m also never sure when I read these things; is the amount of CO2 listed for a flight split between the number of passengers?
That one was listed "per 100 * p * km", so that is per person (and per distance).