Toyota recalled nearly three million RAV4 sport utility vehicles worldwide on Thursday, saying their rear seatbelts could be severed in a crash, leaving passengers unprotected. The fault is suspected in the separation of seatbelts in two crashes, one of which killed a passenger. Although the recall affects only a single model, it follows a disturbing series of discoveries over the last year of flaws in crucial auto safety equipment. Most notable were tens of millions of faulty airbags, some of which led to fatal accidents.