Hi Makoto ,
Yes, if you would use Auto-Focus camera it would be very blurry (see here). You should also keep in mind that high-res color cameras are rolling shutter (not global shutter), which can lead to additional "blurriness" at high speeds. Otherwsise I see no issue of having OAK on the bumper. Here's a video that uses OAK-D inside a camera (not on a bumper though) on a highway. Thoughts?