萊克 (Liker) 教授 : 持續改進與尊重員工是豐田精神的兩大支柱，豐田方法是加速過程、減低浪費、及改進品質的激進式系統 (radical system for speeding up processes, reducing waste, and improving quality)。
豐田 4P 模型：
哲學（理念）(Philosophy)
過程 (process)
人員（員工與夥伴） (people and partners)
解題 (problem solving)
1. 理念為基礎 (Philosophy as the Foundation)
原則 1：管理決策以長期理念為基礎，即使因此犧牲短期財務也在所不惜。(Principle 1: Base your management decisions on a long-term philosophy, even at the expense of short-term financial goals)
2. 好的過程產生好的結果 (The right process will produce the right results)
原則 2：建立連續的過程流動使問題浮現檯面。(Principle 2: Create continous process flow to bring problems to the surface)
原則 3：使用拉式系統避免生產過剩。(Principle 3: Use pull system to avoid overproduction)
原則 4：均衡工作負荷。(Principle 4: Level out the workload) (Heihunka)
原則 5：建立解決問題第一時間就做好的暫停文化。(Principle 5: Build a culture of stopping to fix problems, to get quality right the first time)
原則 6：標準化工作是持續改進與員工授權的基礎。(Principle 6: Standardized tasks are the foundation for continous improvement and employment empowerment)
原則 7：運用視覺控制使問題無法遁形。(Principle 7: Use visual control so no problems are hidden)
原則 8：員工與過程只使用可靠的及測試完全的技術。(Principle 8: Use only reliable, thoroughly tested technology that services your people and processes)
3. 發展員工與夥伴為組織增加價值 (Add value to the organization by developing your people and partners)
原則 9：培養徹底瞭解工作、實踐哲學、及教導他人的領導者。(Principle 9: Grow leaders who thoroughly understand the work, live the philosophy, and teach it to others)
原則 10：發展遵循組織哲學的優秀人員與團隊。(Principle 10: Develop exceptional people and teams who follow your company's philosophy)
原則 11：重視擴大的合作夥伴與供應鏈網絡，激勵及協助他們進行改進。(Principle 11: Respect your extended network of partners and suppliers by challenging them and helping them improve)
