In all, the railroad required five switchbacks, a tunnel and extremely high trestles to make the ascent to Crown King.

Such an extension would require a U-shaped tunnel passing through the Pottinger Peak.

This system requires a deep tunnel that's built in a firm rock.

His second route was decided on but required a tunnel through the chalk hills; work on this did not start until 1819.

Since the proposal would have required a tunnel through a ridge, this plan was soon dropped.

This route required a tunnel at Oxenhall, and another act of parliament was obtained in 1793 to sanction the new route.

Extension of the line onwards from Blankenese station would have required a tunnel.

Its route required a tunnel to be dug directly underneath Devizes Castle.

The ruling grade would have been about 1:60, and would possibly have required a second short tunnel to pass through a spur.

A partial solution that did not require a new tunnel opened on October 13, 2009, after fast-track construction using federal stimulus money.