Complex sentence: The base tunnel bypasses most of the Gotthard Railway, a winding mountain route opened in 1882 across the Saint-Gotthard Massif, which is now operating at capacity, and establishes a direct route usable by high-speed rail and heavy freight trains.
Split into simpler sentences: The base tunnel bypasses most of the Gotthard Railway, a winding mountain route opened in 1882 across the Saint-Gotthard Massif, which is now operating at capacity. It establishes a direct route usable by high-speed rail and heavy freight trains.