Train projects could give London a £12bn annual boost

London scored well for its comprehensive Tube network and the congestion charge, but was criticised for overcrowding and a housing shortage that was creating longer journeys for commuters.

Speaking at the World Cities Summit in Singapore, Dr Roland Busch,

Dr Roland Busch, Siemens chief executive for Infrastructure & Cities said the worldwide urban population boom meant cities had to invest in transport and it was a "fairytale" to suggest there was insufficient funds.

Speaking at the World Cities Summit in Singapore, he said: "The study is about giving an idea of the benefits of proper investment infrastructure; its about stimulating discussion on how our cities need to invest. When im talking to mayors they ask me how they can justify spending billions on a metro line and this study is a first shot at helping them argue that case.

Its a fairytale to say that cities don't have the money to spend. They have to in order to feed the engine of economic growth. We are going for funding models where we are using banks to help get the financing and we also realise that a lot of pension funds that used to buy government bonds don't see the yield so they are looking for a long term investment with a decent return and low risk they end up with (transport)."

According to Credo, the study is the most detailed of its kind to look into the economic benefits of transport investment, and the cost of failing to spend.

It rated Copenhagen as the best-value public transport system with Singapore ranked first among smaller cities. Chris Molloy, the study's author, measured journey times, reliability, fares, network density and crowding to assess the impact on a city's productivity, although he admitted it was "not an exact science".

He said: "All cities can learn from the leading cities in their category in order to close the gap on their transport network's efficiency, reduce costs and increase productivity. The more efficient a city's transpirt network is, the more attractive it is to business and people."

But to achieve that boost in London, the mayor must find ways of funding transport improvements even beyond committed major projects such as the upgrade of the Tube and crossrail 1.

The mayor has championed Crossrail 2 as a means of complementing crossrail 1 - to open in 2018 - and absorb passengers arriving in London on HS2.

As well as rubber-stamping Crossrail 2, London needs to boost bus capacity the report said.

In the study, London scored well for the Tube's comprehensive network; the congestion charge. But a shortage of housing is forcing commuters into longer journeys while peak time overcrowding on tube and rail and high fares were pinpointed as weaknesses.