Complex sentence: The Expo Line ran only as far as New Westminster Station until 1989, when it was extended to Columbia Station and in 1990, once the Skybridge was finished, it continued across the Fraser River to Scott Road in Surrey.
Split into simpler sentences: The Expo Line ran only as far as New Westminster Station initially. In 1989, it was extended to Columbia Station and in 1990, once the Skybridge was finished, it continued across the Fraser River to Scott Road Station in Surrey.