Complex sentence: The RER is operated partly by RATP, the transport authority that operates Paris Métro, and partly by SNCF, the national rail operator; however, the system uses a single fare structure and no transfer is needed between parts run by the two operators.
Split into simpler sentences: The RER is operated partly by RATP, the transport authority that operates Paris Métro, and partly by SNCF, the national rail operator. In spite of this, the system uses a single fare structure and no transfer is needed between parts run by the two operators.