Complex sentence: At its height in the 1920s, the railway was carrying well over a million passengers a year carried in up to 15 round trips on the Peel and Port Erin lines, and up to 12 on the Ramsey line.
Split into simpler sentences: At its height in the 1920s, the railway was carrying well over a million passengers a year. The high-season timetable consisted of up to 15 round trips on the Peel and Port Erin lines, and up to 12 on the Ramsey line.