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.
HH Tunnel The HH Tunnel is a proposed tunnel, actually several tunnels, under Øresund between Helsingborg, Sweden and Helsingør, Denmark. The connection is planned for both road traffic, freight trains, and passenger trains.