Complex sentence: The footbridge between the two platforms (the only one on the island) and the signal box remain but a turntable, sidings and goods yard have disappeared, the latter two under a car park.
Split into simpler sentences: The footbridge between the two platforms (the only one on the island) and the signal box remain from the original configuration. However, a turntable, sidings and goods yard have disappeared, the latter two under a car park.