In Spain, there has been a shift from driving or flying to train travel, since the high-speed rail connection, the Alta Velocidad Espanola, opened in 2008.

The 520-kilometre journey between Madrid and Barcelona that takes six hours by car can now be completed in just 2 hours and 38 minutes by train.

The train, which travels around 300 kilometres an hour, now carries most of the passengers who used to complete the trip by plane.

Early this year the number of train travellers on the route surpassed air travellers, creating political benefits for Spain, which like other European Union countries has set out to lower its carbon dioxide emissions by 20 percent over 10 years.

Analysts say that such emissions per passenger on a high-speed train are about a quarter of those generated by flying or driving.