Unit 9　Wheels

No matter where you are，all big cities around the world have traffic jams these days.But although they all have their problems，many cities also have a type of transport that has become a cultural icon(文化标识)． In London，to avoid the traffic above ground，people use the“underground”，also called the“Tube”．The city has the oldest and most complicated(混乱的) underground railway system in the world and is the pride of many Londoners.With 12 lines and 275 stations across the city，the Tube，is normally the quickest and easiest way of getting around London.In London，you are never far from a Tube station.