As the Semmering is a major bottleneck in the Austrian railway network, the Semmering Railway, which is a UNESCO World Heritage site, is planned to be supplemented by a tunnel at the base of the mountains. The project is supported by the Austrian Federal Government and the governments of Styria and Carinthia, but has been heavily opposed by the government of Lower Austria, which stalled the project by issuing negative environmental impact statements. The project has now been revised according to the advanced state of technology and the layout of the line has been altered in order to minimize effects on ground water.