I believe I found Devilstower's diary.  A back of the envelope calculation shows how much difference these steps would have made. ~1/3 of all CO2 emissions come from transportation, if fuel economy was conservatively 3 times what it is today, we would emit ~20% less CO2 than we are emitting now. This may have given us a shot at avoiding a 2 degre C warming by the end of this century, and we would have accomplished 1/4 of the emissions reduction necessary by 2080.