sentences:  Around 20 tunnels will need to be modified in order to ensure that semitrailers with a four-metre headroom can be transported on rail wagons.Changes will also need to be made to some 80 platform roofs and sets of signals.In Switzerland, freight traffic is handled at the three large marshalling (shunting) yards at Basel-Muttenz, Zurich-Limmattal and Lausanne-Triage.