The world's longest and most expensive rail tunnel has opened in Switzerland

The trains will be able to travel at speeds of up to 250 kilometres an hour, reducing the journey times between Zurich, Switzerland, and Milan, Italy, from just over four hours - to two-and-a-half hours.

It has taken 17 years to build and the whole project was delivered on time and on budget.

Thomson Reuters correspondent Michael Shields told Rachel Smalley the planning for the tunnel began in early 1990.

"The interesting thing in my view is it's the Swiss voters who decide practically everything in this country under the system of direct democracy, who supported it from the word go - and even sometimes over the objections of the Government and parliament."

LISTEN ABOVE: Michael Shields speaks with Rachel Smalley