What tunnel runs under the Hudson River and has a ventilation system innovated by Ole Knutsen Singstad?
Ole Singstad Ole Knutsen Singstad (June 29, 1882 – December 8, 1969) was a Norwegian-American civil engineer who innovated the ventilation system for the Holland Tunnel (which subsequently became commonly used in other automotive tunnels) and advanced the use of the "Sunk-tube" method of underwater vehicular tunnel building, a system of constructing the tunnels with prefabricated sections.
Lopper II Rail Tunnel The Lopper II Rail Tunnel is a railway tunnel in the canton of Nidwalden in central Switzerland. It forms part of the Zentralbahn Luzern–Stans–Engelberg line, which links Lucerne with Engelberg, between Hergiswil station and Stansstad station. It is 1743 m in length, and carries metre gauge () track electrified at 11 kV AC 16 2/3 Hz using overhead catenary. The tunnel runs under the Lopper, a shoulder of Mount Pilatus which extends into Lake Lucerne, and immediately on leaving the tunnel the line crosses a bridge over the Alpnachersee arm of Lake Lucerne before entering Stansstad station.