Abstract: A modular assembly line system is proposed having transport means for the transport of workpiece carriers (64) receiving parts or components and having processing stations (61, 62) arranged one behind the other in the direction of conveyance, wherein the transport means have a main circulating path (10) composed of main circulating path segments arranged one behind the other and secondary path segments (31 to 37) which can be branched off from the main circulating path segments, and the secondary path segments (31 to 37) each have a feed-out section (42) and a feed-in section (44) extending transversely to the main circulating path, a secondary transport section (59) being arranged between feed-out section and feed-in section and extending in the direction of conveyance of the main circulating path (10), with the feed-out section (42) and the feed-in section (44) having opposite directions of conveyance and with the main circulating path segments and/or the secondary path segments accommodating at least one p