I found it here: https://ourworldindata.org/emissions-by-sector

Not sure how reliable all this is... Yet it seems "road" is nearly 10-11% which is big enough to solve and to have already an impact in everyday life. Then it cascades to other sectors too.

That visual shows that road transport is 11% , making it the second highest category, as the poster said. This is a great graphic though, thanks for sharing!

Edit: actually in the graphic it's the largest sector! My bad