"Passenger cars are responsible for 12 percent of greenhouse gs emisions in Europe...and up to 50 percent in some car-intensive areas in the United States." (source 1) The pollution has gotten so bad in cities like Paris that they have even gone so far as to "...enforce[d] a partial driving ban to clear the air..." (Source 4) The havy car usage that we are accustomed to increases the amount of these harmful gases in the environment.