A method for producing vehicles in which vehicle bodies are conveyed through multiple system zones (12.i, 14.i, 18.i, 20.i) of a production system for producing vehicles, wherein different types of work are carried out on the vehicle bodies in two respective system zones (12.i, 12.i+1; 14.i, 14.i+1; 18.i, 18.i+1; 20.i, 20.i+1) which follow each other, wherein the vehicle bodies are conveyed through the system zones (20.i) of the surface treatment system at least from a corrosion protection treatment to a final assembly using one and the same conveyor system in a surface treatment system for treating the surface of the vehicle bodies ; characterized in that a conveyor system is used, which comprises a plurality of transport carriages , which can be moved in a transport direction on a rail system , wherein each transport carriage comprises a transport carriage chassis and a fastening device for at least one vehicle body which are coupled to each other by means of a connecting device ; and the vehicle bodies are treated in at least one system zone (12.i, 14.i, 18.i, 20.i) in at least one treatment device (20.i-j; 78), which comprises a housing , in which a treatment tunnel with a tunnel floor is accommodated, wherein the tunnel floor comprises a communication passage , and a driving space for the transport carriage chassis exists, which is arranged below the treatment tunnel , such that the transport carriage chassis can be moved within the driving space , wherein the fastening device is carried along in the treatment tunnel , and the connecting device extends through the communication passage . vehicle bodies are conveyed through multiple system zones (12.i, 14.i, 18.i, 20.i) of a production system for producing vehicles, wherein different types of work are carried out on the vehicle bodies in two respective system zones (12.i, 12.i+1; 14.i, 14.i+1; 18.i, 18.i+1; 20.i, 20.i+1) which follow each other, wherein the vehicle bodies are conveyed through the system zones (20.i) of the surface treatment system at least from a corrosion protection treatment to a final assembly using one and the same conveyor system in a surface treatment system for treating the surface of the vehicle bodies ; characterized in that a conveyor system is used, which comprises a plurality of transport carriages , which can be moved in a transport direction on a rail system , wherein each transport carriage comprises a transport carriage chassis and a fastening device for at least one vehicle body which are coupled to each other by means of a connecting device ; and the vehicle bodies are treated in at least one system zone (12.i, 14.i, 18.i, 20.i) in at least one treatment device (20.i-j; 78), which comprises a housing , in which a treatment tunnel with a tunnel floor is accommodated, wherein the tunnel floor comprises a communication passage , and a driving space for the transport carriage chassis exists, which is arranged below the treatment tunnel , such that the transport carriage chassis can be moved within the driving space , wherein the fastening device is carried along in the treatment tunnel , and the connecting device extends through the communication passage . <EOS>