I was driving in the left lane of a two lane street. Due to construction, the right hand lane had orange construction barrels. All of a sudden, alarms went off, in RED LETTERS the word BRAKE! appeared on my dashboard and the car automatically braked - hard. There was no obstruction of any kind in my lane. All the items on my seats flew to the floor. The seat belt wrenched me back. I now have a mild sore shoulder, neck and back. If someone had been following me, they certainly would have hit me due to the sudden, unexplained stop. The incident was very shocking and scary, since there was no obstruction of any kind in my lane, it took me totally by surprise. As I travelled, I was in no danger. The only danger would be if I suddenly stopped, which my car automatically did! I will be sure to turn this "safety" feature off in the future. This was a failure of the automatic Collision Mitigation Braking System (CMBS). The system was activated when no danger was present. I did not contact a mechanic or the manufacturer, as I question whether my complaint would be taken seriously.