About 2.3 million rail passengers have travelled through the new transalpine tunnel in Switzerland over the past eight months, an increase of 30% compared with same period a year ago.
On average, 10,400 people cross the Gotthard base tunnel in central Switzerland every day, according to the Federal Railways.
Some 17,000 freight trains also used the 57km (35.4 miles) tunnel during the eight-month period, officials said on Wednesday.
The world’s longest train tunnel was opened to passenger trains last December. It links the region of Lake Lucerne with canton Ticino in the southern Alps.
The state-run railway company said international train links between Milan in northern Italy and central Switzerland had a punctuality rate of 87.5%.
Owing to high demand, additional regional trains from Ticino had to be laid on for people wishing to travel back north on Sunday evenings.
The main challenges for the cargo business include better coordination with Italy and Germany, increased digitalisation and automation, according to a statement on Wednesday.
North-south train services are expected to become faster from 2020 onwards, when the Monte Ceneri tunnel in Ticino is due to open to traffic.
There are plans to run a regular train service between Zurich and Milan that could cut the journey time from 3.5 hours to 2.45 hours.