Transportation accounts for 30% to 40% of your CO2 output. Go by train or use a bicycle. Drive a small car that doesn ́t need loads of fuel just to carry its own weight around. Drive a motorbike instead of a car. Buy a hybrid car or an electric one. Use a car-sharing system or go social. Drive slowly. It uses far less fuel. With a modern car the difference between fast and slow can be 400 additional kilometres.