Complex sentence: The G7 in question was a four car Tangara set that was fitted with an AC drive system for evaluation purposes, with a driver in the forward driver carriage and a guard in the back driver carriage.
Split into simpler sentences: The G7 in question was a four car Tangara set that was fitted with an AC drive system for evaluation purposes. There was a driver in the forward driver carriage and a guard in the rear driver carriage.