The 21 km of single track, which lack passing loops, greatly complicates operations. Despite its relatively recent completion date, the LBT has already become a major bottleneck for rail freight traversing the Alps. Typically, trains using the LBT are scheduled together in batches that run in each direction separated by long intervals; trains more than seven minutes late are either routed via the old line or must wait for the next available timetable slot in their direction in the LBT, incurring long further delays in either case. By 2019, around 110 trains per day were using the LBT, while a further 66 have continued to use the old mountain tunnel largely due to the base tunnel's current capacity constraints. Of these 110, 30 were passenger services and 80 were hauling various types of freight, including intermodal freight transport and long-distance heavy freight trains. Heavy freight trains up to a maximum weight of 4,000 tons and a maximum length of 1,500 metres have to use the LBT, as they are above the maximum gauge of the pre-existing mountain track. By 2017, the LBT reportedly facilitated the movement of 35.7 million gross tonne of rail freight.