The London Underground, also known as the tube because of the shape of its stations, carried 1.23 billion passengers in 2012 to 2013. It has also been a popular suicide destination since it first opened in the 19th century. The suicide rate reached 25 people per year after 1940, rising to 100 people per year since 1980. Some stops have several drainage channels, which are regarded as "suicide pits" because they have saved many lives.