High-speed rail construction projects have frequently required long tunnels to reduce travel time and distance. The California High-Speed Rail (CHSR) authority is considering a tunnel up to 16 miles long for a direct route from Palmdale to Burbank. With advances in tunneling technology, the many long tunnels in use around the world today hold valuable lessons for CHSR, particularly with respect to minimization of ground disturbance and improved passenger and operator safety. The primary objective of this project is to determine the state of the art for construction and operation of long tunnels used for high-speed rail. With an abundance of long tunnels successfully completed and already in use around the globe, an examination of those projects can provide the State with the benefit of their experience at little cost.

The research began with a review of the literature on long tunnels around the world, with a focus on characteristics and the research team constructed a detailed database of information on the projects behind the world’s long tunnels. Based on the data, this report presents data on 67 tunnels longer than 4.5 miles, including 32 high-speed railway tunnels, located in 28 countries around the world. The research team analyzed the data to determine the factors that should be considered in planning long tunnels for HSR projects. Analysis results were documented in a systematic manner to compare with potential tunnels for the Palmdale-to-Burbank segment of the California HSR system. It is hoped that the trends identified from the aggregate data will help inform decisions for the tunnel projects being considered for the Palmdale-to-Burbank segment of California High-Speed Rail.

Publication Date


Publication Type



Transit and Passenger Rail

MTI Project



Long Tunnel, TBM, Tunneling Method, High Speed Rail, Trend Analysis



1429-long-tunnels-trend-analysis-bf.pdf (403 kB)
Research Brief