Complex sentence: Rapid transit technology describes the use of infrastructure and technology on rapid transit (also called "metro" or "subway" systems), which in has changed significantly over the years since the first underground railway lines opened in London in 1863.
Split into simpler sentences: Rapid transit technology describes the use of infrastructure and technology on rapid transit (also called "metro" or "subway" systems). It has changed significantly in the years since the first underground railway lines opened in London in 1863.