YI Smart Dashcam makes the decision based on the standard lane marks on the road. While testing or using the ADAS, it is better to connect the camera to the APP, switch on the GPS of your phone and drive at the speed of 50 km/h or above. The best performance will be achieved with the help of the speed and GPS information (this function in similar products will normally turn on only when the speed is at 50-60 km/h). It is normal that this function will be affected when the road marks are worn out, unclear or missing, or when the driver switches lanes too quickly.