Turks eager to test out the world’s first continent-connecting tunnel caused caused overcrowding and delays on Wednesday.
Passengers rode to and fro under the Bosphorus, a day after Prime Minister Tayyip Erdogan opened the rail line that connects Asia and Europe.
Authorities said one station was forced to close because of the overcrowding, while there were delays when passengers pressed the emergency stop buttons.
The 13 km (8-mile) tunnel opened to great fanfare on Tuesday, the 90th anniversary of the Republic of Turkey.
It is expected eventually to carry some 1.5 million passengers a day under one of the world’s busiest waterways.