In regards to 4 more than twice as many people take buses trains and the tube than drive cars for commuting. This includes everyone who commutes into the city

In regards to 4 more than twice as many people take buses trains and the tube than drive cars for commuting. This includes everyone who commutes into the city from outside it too so capacity wouldn't need to be doubled. https://londondatastore-upload.s3.amazonaws.com/Zho%3Dttw-flows.pdf https://londondatastore-upload.s3.amazonaws.com/Zho%3Dttw-fl... Also not every increase of capacity costs £20bn. The northern line has increased capacity by 10% by upgrading signalling. New trains will increase it by 10% again.