  We propose a vision-based warning system for the maintenance personnel
working on short-term construction sites. Traditional solutions use passive
protection, like setting up traffic cones, safety beacons, or even nothing.
However, such methods cannot function as physical safety barriers to separate
working areas from used lanes. In contrast, our system provides active
protection, leveraging acoustic and visual warning signals to help road workers
be cautious of approaching vehicles before they pass the working area. To
decrease too many warnings to relieve a disturbance of road workers, we
implemented our traffic flow check algorithm, by which about 80% of the useless
notices can be filtered. We conduct the evaluations in laboratory conditions
and the real world, proving our system's applicability and reliability.
