Complex sentence: For a short while Trewoon had its own train station which was situated by the railway bridge crossing the A3058 accessible only by foot the station was very small and often not used by trains leading to its closure.
Split into simpler sentences: For a short while Trewoon had its own station which was besides the railway bridge crossing the A3058 and accessible only by foot. Tthe station was very small and not often used by trains leading to its closure.