For three years of my life, I biked 8.05 km  every single day during the week.  During the days where I did not feel like biking, I took public transportation which was very convenient since I live 3 blocks away from either the bus or BART station.  Even during the first year and a half during high school, I took the school bus the majority of the time.  However, once I got my license my CO2 contributions increased tremendously.  Based on the test I took, I got a total of 5,126 kg in the transportation section compared to my region (California) with an average of 2,557 kg.  Similar to me, the majority of the people in the United States heavily rely on transportation.  In 2012, 28% of the total US greenhouse gas emissions were due to transportation.  Based on the collected data, transportation was the second largest factor that contributed to the US greenhouse gas emissions.  http://www.epa.gov/climatechange/ghgemi … ation.html On an average day, I travel about 31.8 km as I go from home, to school, to practice, and back home.  (However, I do drive a P rius which is a hybrid car.)  I heavily rely on transportation by car every single day because it is how I travel from place to place.  I know there are alternative ways to decrease my CO2 contributions in terms of transportation, but I cannot legally do so.  To be more specific, in California, USA, teenage drivers are not allowed to transport anyone under the age of 25 until he or she has had a license for more than a year.  This law limits my options and I cannot do much about it.  When I get the chance to do so, I will form a carpool and decrease any unnecessary CO2 being added into the atmosphere.  But for now, driving is "off the table" when it comes to carbon emissions.