Planning your big summer vacation? If you believe half the fun is getting to your destination, consider using trains instead of airplanes for your trip. While it may take longer to get there, train travel has a much lower carbon footprint than flying on a gas-guzzling plane. According to the International Energy Agency, car travel accounts for 71 percent of CO2 emission, planes account for 12.3 percent and railways just 1.8 percent. So go green and embrace the romantic and fun idea of seeing America by rail.