问题描述：
英语翻译
which are semi-permanently coupled into sets;these sets may be joined together to form larger trains,but usually passengers can only move around between cars within a set.This "closed"nature allows the separate sets to be easily split to go separate ways.Some multiple-unti trainsets are designed so that corridor connections can be easily opened between coupled sets; this usually requires driving cabs either set off to the side or above the passenger compartment.
which are semi-permanently coupled into sets;these sets may be joined together to form larger trains,but usually passengers can only move around between cars within a set.This "closed"nature allows the separate sets to be easily split to go separate ways.Some multiple-unti trainsets are designed so that corridor connections can be easily opened between coupled sets; this usually requires driving cabs either set off to the side or above the passenger compartment.
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