At 100 MPH, a vehicle would travel 147 feet per second. With a camera operating at 60 fps, capturing two frames for motion estimation, the object in the camera would travel around 9.7 feet. If the object is 100-200 feet away, it's not too big a deal. At 300 feet per second, that object travels 20 feet in the same 2-frame span. There aren't too many situations in which two vehicle approach one another with a speed difference of 300 feet per second, so that would be a pretty rare case. But even still, with the object covering only 20 feet of distance, the system could have worked out what it is, where it is, where it's headed, and how fast it's getting there.