Merits : It partly solved the housing crisis by carrying large masses of people to and from the city. When the first section of the underground in the world opened on 10 January,1863, it carried 10,000 passengers, with trains running every ten minutes.By 1850, the trains were carrying 40 million passengers a year.By the 20 th century, most large metropolises such as New York, Tokyo,Chicago had indispensable metro services. The population in cities became more dispersed. Better planned suburbs and a good railway network enabled large numbers to live outside central London and travel to work. Drawbacks : They created more pollution and were considered by people to be a menace to health. Passengers complained of smoking pipes, an atmosphere which was a mixture of sulphur, coal dust and foul fumes causing asphyxiation.Many called the the trains ‘‘iron monsters’’ adding to mess and unhealthiness. To make two miles of railway, 900 houses were knocked down. It led to a displacement of the London poor, specially between the two wars. They wore down social distinctions but also created new ones.