How Edinburgh's '˜bigger trams' may have increased costs

In written evidence to the inquiry, former project manager of Transdev, which provided technical and operational advice, revealed that tram firm TIE had not accepted Transdev’s advice on the size of trams and instead opted for longer vehicles.

“The original concept was to have ‘normal’ sized trams of about 30m length operating at eight trams per hour on the route to the airport, a service interval of one tram every 7.5 minutes.

“Lothian Buses argued that a service interval of 10 minutes was needed in Edinburgh but their rationale was never made clear to me.

“Transdev argued against this from their experience elsewhere and from established tram business case principles. The decision was made at board level with no representation present from Transdev. Lothian Buses were present. Lothian Buses had their way.”

Mr Harries said he believed the decision had led to “significantly more intrusive and costly infrastructure, with tramstops needing to be 10m longer and having a greater Impact on the city”.

He said it had also limited the available locations for tramstops and meant design constraints on the highway where longer trams could not be permitted to obstruct junctions .

“Some tram suppliers may have been unwilling to bid for the contract, leading to potential cost increases.”

And he said it also meant increased demand on the power supply system, leading to increased infrastructure costs and energy costs.