Question

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

Answer 1

Seikan Tunnel that connects the islands of Honshū and Hokkaidō
Seikan Tunnel 53.85 km (33.46 mi); Channel Tunnel 50.45-kilometre (31.35 mi); Gotthard Rail Tunnel 15 km (9.3 mi); Simplon Tunnel 19.803 km (12.3 mi). The Gotthard Base Tunnel two tubes (railway twin tube), opened and first used in 2016, are 57.104 km (35.5 mi) and 57.017 km (35.4 mi).