Traffic is one of the biggest carbon dioxide emitters in the world. When too much carbon dioxide and other greenhouse gases get to the atmosphere of the Earth, they cause global warming. Because of global warming, consumers and the government forces companies to behave in a more environmentally friendly manner than before. Red One Plus Ltd is a charter bus company. They have new buses with low emissions and low energy consumption. The buses are equipped with Euro 4 engines. The company choose the bus for a trip according to how many customers there are joining. Red One Plus Ltd wanted to know what they could do to become greener and they were concerned whether their customers are satisfied.