The privileged transit traffic or corridor traffic is traffic of one country across the territory of another country without usual customs and passport checks. The corresponding line of communication (usually a railway) is called the (privileged) traffic corridor and a train used in this kind of transit is called a corridor train (German: Korridorzug, Italian: Treno-corridoio).
A famous historical case of privileged transit was the arrival of Vladimir Lenin in a "sealed train car" from Germany to Russia in April 1917, amid World War I and Russian revolutionary activity.