Disclaimer: I work for GM, any opinions are solely my own. This is enormously context-sensitive, but it is not at all odd to have a buffer with several hours w

Disclaimer: I work for GM, any opinions are solely my own. This is enormously context-sensitive, but it is not at all odd to have a buffer with several hours worth of vehicles in auto assembly, for example between shops (ie between body and paint and between paint and final assembly). As you get closer to the end of the line, the buffers get much smaller, but you may have a 5 minute buffer between the last few lines in Final Assembly. One other thing to point out here; The two main styles of conveyance in vehicle assembly are fixed position stop and stop stations (also known by many other names). - Fixed position stop is what you call rigid line, and it is used where humans work on cars. The conveyor runs at a constant, slow speed through constant size work areas called footprints, such that each worker gets about a minute or so to do a set of assembly tasks. Humans can attach parts as the vehicle moves down the line. With fixed position stop, there is no buffer as the vehicle carriers are physically connected to a conveyor chain. - Stop stations are used where robots work on vehicles. It is very difficult to get a robot to work on a moving vehicle (but possible). Generally these conveyors move about twice as fast as the rigid stations, but all work is done while the vehicle is stopped. Also, each vehicle moves independently between stop stations as fast as the conveyor can move, and there is some buffering between each station. > 20 minutes of buffer in an auto plant? That's a building the size of a large supermarket. Yes, but it's in a mezzanine above the work area.