you are forgeting about the blind spot detection system! it uses radar also. when my son or wife follows me their V1 goes nuts. When i go past large objects close to the road it will bounce back and set off my V1 also.
2009 750Li - Space Grau Metallic, Camera pkg, Conv pkg, Driver Asst pkg, Lux Seat pkg, Lux rear seat pkg, Prem sound pkg, Sport pkg, HUD, Massaging rear seats, Smartphone integration, Sat radio, MTEC H8 4750K Halo lights