Las Raíces Tunnel

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Las Raíces Tunnel (Spanish: Túnel Las Raíces) is a tunnel located in Chile's Araucanía Region, linking the communes of Curacautín and Lonquimay, in upper Bío-Bío River, through the Las Raíces Cordillera; 1,010 m above sea level. With a length of 4,528 m; it is the longest road tunnel in South America.

Feasibility studies began in 1911, with final blueprints ready in 1929. Construction lasted eight years, from 1930 to 1938, with an investment of more than 32 million Chilean pesos of the time. It has a width of 4.2 m and a height of 5.6 m. A railway was constructed in 1956.

The tunnel is part of the motorway 181 that links the town of Lonquimay with Curacautín. The 181 route then continues to Argentina through the Pino Hachado Pass in the Andes mountains. As such, the tunnel serves as a link between the Pacific and Atlantic Oceans, from Lebu, in the Biobío Region of Chile to Bahía Blanca in Argentina.

The tunnel allows only one-way transit so vehicles have to wait for the transit direction to change. Despite of not being asphalted the tunnel is passed daily by heavy fuel trucks coming from Argentina. It has an average daily traffic of about 450 vehicles.