Is the Silvertown tunnel a bridge to the future or a step backwards?

As the £2.2bn tunnel prepares to open, opinions are divided: will it reduce congestion, or is it a relic of transport planning that worsens pollution?From high above the Thames, the distinctive portals of the new Silvertown tunnel are clearly visible: a black arch on the North Greenwich peninsula, a green conical building a mile across the water in Newham.On Monday, tens of thousands of cars and lorries will start passing between them, almost directly below the cable car built by Boris Joh