via Lean Manufacturing Blog, Lean at NUMMI (site broke the link so I removed it) by Patrick Waurzyniak , Manufacturing Engineering. An article well worth reading.
NUMMI’s production system is patterned closely after TPS, which is constantly changing and being updated, notes Gonzalez-Beltran. The pillars of TPS are the waste-reduction techniques of Just-in-Time production, bringing inventory to where it is needed and at the right time, and also jidoka, which provides machines and operators the ability to detect abnormal conditions and immediately stop work if such conditions occur. Other major lean manufacturing elements being emphasized at NUMMI include standardized work, kaizen events, jishuken (an in-depth week-long workshop similar to a kaizen event), and value-stream mapping, which NUMMI has pushed down into its supplier companies.