According to the California DMV [PDF], one of Apple's self driving test vehicles was involved with a minor accident on September 27.
The self-driving car, which was in autonomous mode at that time, hit a curb and went 13 miles an hour. The car was not damaged, but it did need to be realigned.
Sunnyvale, California: A test vehicle was operating in autonomous mode and turned right from Mathilda Avenue onto Del Ray Avenue. It made contact at 13 miles an hour with a curb. The contact caused misalignment, but there was no damage to the tires or wheels. There were no other agents involved and there were no reports of injuries. Law enforcement was not dispatched to the scene.
The accident occurred as the vehicle was turning left from Mathilda Avenue onto Del Ray Avenue. This is right next to Apple's Mathilda Avenue address.
Several minor accidents have occurred with Apple's self driving vehicles, but these were caused by other drivers while they weren't in autonomous mode. This is the second incident in which an Apple vehicle was operating in autonomous mode.
Apple has been testing its self driving software since early 2017 using the Lexus RX450h vehicles equipped with sensors and cameras. This was done in the vicinity of its Cupertino campuses. Apple's long-term car project includes autonomous driving work. Rumours suggest that Apple will release a vehicle in the middle to late 2020s.