Complex sentence: Transwa services diverge and continue to Kalgoorlie (the Prospector) and to Merredin (the Avonlink), when trains arrive at Perth they continue through to the Fremantle Line.
Split into simpler sentences: Transwa services diverge and continue to Kalgoorlie (the Prospector) and to Merredin (the Avonlink). When trains arrive at Perth they continue through to the Fremantle Line.