The sixteen vehicles (paths or systems)
From The Treasury of Philosophical Systems by the Omniscient Longchenpa, the sixteen vehicles (paths or systems) are presented as follows:
I. Worldly Vehicles
The vehicle of the gods
The vehicle of humans
II. Non-Buddhist (Outer) Philosophical Systems
3. The system holding the view of eternalism
4. The system holding the view of nihilism
III. Inner Buddhist Systems – Common (Śrāvaka) Vehicles
5. The Śrāvaka (Hearer) vehicle
6. The Sūtra-based school (Sautrāntika)
IV. The Great Vehicle (Mahāyāna)
7. The Mind-Only school (Cittamātra / Yogācāra)
8. The Middle Way school of Autonomous reasoning (Svātantrika Madhyamaka)
9. The Middle Way school of Consequence (Prāsaṅgika Madhyamaka)
V. The Secret Mantra (Vajrayāna)
A. Outer Tantras
10. Kriyā Tantra (Action Tantra)
11. Caryā Tantra (Conduct Tantra)
12. Yoga Tantra
B. Inner Tantras
13. Mahāyoga
14. Anuyoga
15. Atiyoga — the vehicle of spontaneously present, luminous clarity