The mode of transport matters. The largest possible carbon footprint would in be something like a cross country flight in an ICE flying car like a (vaporware)

The mode of transport matters. The largest possible carbon footprint would in be something like a cross country flight in an ICE flying car like a (vaporware) Moller. Trains run 6-60 g/km whereas single-passenger vehicles are 90+. The smallest might be in a solar-powered glider or solar-powered "car", effectively 0. Also, if you can personally offset your footprint by actively participating in carbon capture and sequestration permanently, then some luxuries are okay in small quantities.