Major transport schemes including the refurbishment of New Street Station and Birmingham International Airport’s runway extension will boost businesses and the regional economy by almost £1.5 billion in the first 12 years of operation, new research has found.

The figure is about a third higher than previous estimates, according to a study by economists at the West Midlands Regional Observatory.

Benefits include improved journey times for freight and cars, increased competitiveness for businesses and better labour force mobility.

The figure of £1.5billion would be achieved between 2011 and 2023, assuming the station and airport schemes go ahead as planned and on time along with proposals to add lanes to sections of the M6, M5 and M42 around Birmingham and improvements to the rail freight network.

Past calculations have put the value to the economy of the schemes at £1.1billion.

But the latest report says that figure was an under-estimate because it failed to recognise most benefits accrue in the first 20 years after infrastructure projects are completed.

The report sets out the business cases for four projects:

* New Street Gateway – will unlock significant economic benefits in addition to supporting Birmingham as a world city

* Birmingham International Airport – runway extension will give businesses direct access to China, India and the west coast of America

* Birmingham Box – active traffic management and widening of sections of the motorway network around Birmingham will ease congestion

* Rail Freight Upgrades – improvements to routes between Southampton and Birmingham and Nuneaton and Peterborough will assist export markets

Only one of the schemes, New Street Gateway, is certain to go ahead.

The runway extension is subject to obtaining planning permission while the motorway and rail improvements require government approval.

BIA’s runway extension is expected to produce the largest benefit of all the schemes, ploughing £1.8billion into the economy over a 40-year period.

New Street Gateway will be worth £2.1billion but over a 75-year period.

The report adds that the four schemes can play a significant role in closing the annual £10billion gap in economic output between the West Midlands and other English regions.

Birmingham Chamber of Commerce and Industry chief executive Jerry Blackett, who chairs the West Midlands Business Transport Group, said the analysis would provide extra ammunition when it came to convincing ministers of the case for major regional infrastructure improvements.