User: Which is the best tube line?
Assistant: The London Underground has many lines that are popular for different reasons. The Victoria line is one of the fastest with the most convenient stops although it is noisy and lacks air conditioning. The Hammersmith, Metropolitan and Circle line have air conditioning making them popular in summer. Although not technically part of the London Underground, the Docklands Light Railway has a very scenic route when viewed from the front seats of the driverless trains. The Elizabeth Line is also popular, although technically not an underground line, due to it's new trains, stunning station architecture and faster routes.