Complex sentence: The station will feature a double-island interchange layout, with Line 4 trains on the outside and Line 9 trains on the inside, which will allow most riders to change lines simply by crossing the platform, instead of walking between levels.
Split into simpler sentences: The station will feature a double-island interchange layout, with Line 4 trains on the outside and Line 9 trains on the inside. Which will allow most riders to change lines simply by crossing the platform, instead of walking between levels.