The Principles of the Toyota Production System can be summarized into four basic rules. The rules given below are the results of observations and research completed by Steven Spear and H. Kent Bowen.1


  1. All work shall be highly specified as to content, sequence, timing, and outcome.
  2. every customer-supplier connection must be direct, and there must be an unambiguous yes-or-no way to send requests and receive responses.
  3. The pathway for every product and service must be simple and direct.
  4. Any improvement must be made in accordance with the scientific method, under the guidance of a teacher, at the lowest possible level of the organization.

1 Spear, Steven and H. Kent Bowen (1999), "Decoding the DNA of the Toyota Production System," Harvard Business Review, vol. 77, no. 5, Sept-Oct; pp.97-106.