Congestion is an issue in Aberdeen

But now Aberdeen University's Andrew Hurst has suggested that a tunnel would be a more effective solution.

He said: "It would obviously be much shorter because it can go in a straight line .

"In the north it could enter the city at the River Don and exit it at the River Dee.

"The only environmental impact would be at the entry and exit points of the tunnel."

Aberdeen's granite would not be an obstacle either, because Mr Hurst said it is ideal for a tunnel and would also produce much-needed aggregate.

Aberdeen's politicians and business leaders lobbying for a bypass said the tunnel is an idea worth looking at because it has potentially less impact on the environment.