I was looking to pass traffic in front of me when traffic stopped. There were a few cars that drove into the emergency lane I saw in the review mirror.
My Toyota Tundra 4x4 TRD Pro has a similar alarm to warn me of someone stopping quickly ahead of me. I also didn't know it was there and it frightened the crap out of me when it happened for the first time, it's much louder than this one. :(