ARLBERG TUNNEL, part of the Arlberg railway con necting the Vorarlberg (q.v.) with Innsbruck in the Tirol. It was opened in pierces the Arlberg Alp from Langen to St. Anton, is over 6m. long, and ascends as high as 4,3ooft. It cost £1,5oo,000 to construct, and was electrified in 1923.