Complex sentence: The system uses a mix of Adtranz C-100 and Bombardier Innovia APM 100 vehicles to carry passengers to departure gates; unlike the similar Gatwick Airport transit, the Stansted transit is only accessible "airside" (i.e. only after passengers pass through security).
Split into simpler sentences: The system uses a mix of Adtranz C-100 and Bombardier Innovia APM 100 vehicles to carry passengers to departure gates. Unlike the similar Gatwick Airport transit, the Stansted transit is only accessible "airside" (i.e. only after passengers pass through security).