Since the early 2000s, high-speed trains have become popular in Europe and Asia. These trains can travel at more than 300 kilometres an hour. For passengers, the journey is fast and comfortable, because modern carriages are designed to be soundproof. However, the problem for engineers is the loud noise outside. People living near the railway often complain about it. The trains are usually built with the help of the latest technologies and require expensive equipment. Nevertheless, they are considered to be more efficient than cars and planes, because they save time and reduce pollution. In the future, high-speed railways may connect most European capitals.