Complex sentence: By 1985, single track for almost its entire length it was handling 19 million tons of coal-but implementation of the second stage of the Clean Air Act (1990) meant that demand for clean coal would rise quickly.
Split into simpler sentences: By 1985, the line was single track for almost its entire length, and it was handling 19 million tons of coal. The implementation of the second stage of the Clean Air Act (1990) caused demand for clean coal to rise quickly.