Ole Knutsen Singstad (June 29, 1882 – December 8, 1969) was a Norwegian-American civil engineer best known for his work on underwater vehicular tunnels in New York City. Singstad designed the ventilation system for the Holland Tunnel, which subsequently became commonly used in other automotive tunnels, and advanced the use of the immersed tube method of underwater vehicular tunnel building, a system of constructing the tunnels with prefabricated sections. He also designed the Lincoln Tunnel, Brooklyn–Battery Tunnel, and Queens–Midtown Tunnel. By 1950, Singstad had designed and overseen the construction of more underwater tunnels than all other engineers combined. In 1946, the Triborough Bridge Authority under Robert Moses took over tunnel construction in New York, and Singstad was subseque