When the Simplon Tunnel opened it was the only permanent road access between which two countries?

Question

Until the Gotthard Base Tunnel was commissioned in 2016, what was the world's longest traffic (railway or road) tunnel?

Answer 1

Italy and Switzerland
The first of its two single-track tunnels was opened in 1906, and is 19,803 m (64,970 ft) long. The second, 19,824 m (65,039 ft) long, was opened in 1921. For much of the 20th century the tunnel was the longest railway tunnel in the world.