QUESTIONS have been raised about the environmental credentials of the Edinburgh trams after it emerged they will only reduce deadly emissions by one per cent and will increase traffic on some streets.

Edinburgh City Council, which has lauded the environmental benefits of the flagship project to investors and taxpayers, was also criticised for using an impact assessment that is 14 years out of date.

Read more: Edinburgh Tram Inquiry: Chief admits he didn't know who was in charge

Malcolm Reed, a former head of Transport Scotland, said that he warned the council’s trams firm against attributing “additional environmental benefits from the tram project when in fact analysis suggested otherwise”.

The council has confirmed it is using a 2003 report from Transport Initiatives Edinburgh, the axed arms-length company set up to deliver the trams which were finished three years late at a cost of £776 million, more than £200m over budget.

The Herald: Edinburgh Tram Inquiry before Lord HardieEdinburgh Tram Inquiry before Lord Hardie

It comes as residents in the West End and Leith raise concerns over air pollution caused by displaced traffic alongside the tram route.

Tory councillor Nick Cook said the new £165m project which would extend the line from York Place to Newhaven should be shelved until the findings of Lord Hardie’s investigation into the initial line is completed.

Read more: Edinburgh Tram Inquiry: Chief admits he didn't know who was in charge

Mr Reed, who headed up Transport Scotland between 2005 and 2009, raised his concerns in a written statement to the Edinburgh Tram Inquiry which is probing what went wrong on the initial project.

He said: “One of the intended economic outcomes of the construction of the tram was to increase business activity in the areas affected.

“Since it was presumed that businesses would enjoy a boost across the local area because of the tram project, more travel would be generated.

“However, because some of that additional travel would be by car, carbon emissions might go up rather than down because of the tram, an adverse environmental outcome.

“This was a good example of an unanticipated effect, and Andy Park (one of Transport Scotland’s economic analysts) was being robust in his analysis by identifying that Tie should not attribute additional environmental benefits from the tram project when in fact analysis suggested otherwise.”

Councillors last month approved a three-mile extension of the tram network from York Place to Newhaven.

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The council has confirmed the 2003 report was the basis of its environmental assessment for that proposal. It is suggested there are "no unacceptable environmental impacts" for the tram route.

The summary of the 2003 Tie Environmental Impact Statement states that by 2026 there "should be a small net reduction in emissions equivalent to approaching one per cent of current emissions from the area's road networks".

“Over the wider area of the city, road traffic changes caused by line one will lead to improvements in air quality in some areas and reductions in others."

But it adds: "On the majority of road links there will be very little, if any, change.

“The benefit is less in 2026 as traffic congestion increases.”

Meanwhile, the council’s inward investment arm Invest Edinburgh claims to investors: “Edinburgh’s trams offer an efficient and sustainable transport system.

“The trams are also expected to make a positive contribution to the city’s natural environment by encouraging people to shift from car to tram use and so help to ease future traffic congestion.

“There is also expected to be a net improvement in air quality across the city as a whole, as a result of the introduction of the tram.”

Read more: Edinburgh Tram Inquiry: Chief admits he didn't know who was in charge

Dr Ashley Lloyd, former chairman of the West End Tram Traffic Workshops, said that “the extension of the tram down Leith Walk does nothing to improve the fundamental issues we have been raising for nearly a decade - taking polluting traffic from commercial streets into residential areas necessarily impacts the city’s residential exposure to pollutants, and will do so again in Leith”.

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Harald Tobermann, of Leith Central Community Council, said he was astonished the 2003 report was used, adding “there are so many parameters that need to be taken into account – lower emissions per mile for modern buses and cars, larger local population and most importantly: additional emissions during the construction from delays and construction traffic”.

Transport Convener Councillor Lesley Macinnes, pictured below, said: “Increased reliance on trams will help us improve Edinburgh by providing efficient, sustainable transport solutions.

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"With our population growing rapidly – more than 38,000 extra households (a 16 per cent increase) are expected by 2032, a quarter of which are forecast for the Leith Docks and Western Harbour area – we simply must act now to ensure we can cater for more and more people travelling across the capital for work, study or leisure.

"Without trams, congestion is sure to worsen, with more motorised vehicles on our roads.”