What is the legal status of 'lane splitting' (riding between two occupied lanes of moving traffic or filtering between rows of cars) under Chinese traffic regulations?

1. Permitted at all times on all urban roads
2. Permitted only if riding below 30 km/h
3. Permitted for Class D three-wheeled motorcycles only
4. Prohibited; motorcycles must occupy and maintain a single lane like other motor vehicles (不得穿插车流)