Watch a drive and mark each sign as you draw level with it. That one habit is what makes this better than the detector: at the moment you are beside a sign, the car's own GPS fix is the sign's position and the car's course is the direction the sign faces — no guessing how far ahead it was from how wide it looked.
Showing the 60 least-mapped of 766 drives.
107 more finalized drives are not offered — their metadata names segments but the recording is no longer on disk.