The Construction Ahead signs provide advance warning of a major work zone. These signs are generally used on long-term construction projects where drivers may encounter various construction activities.

The CS-33 sign is installed in advance of the approach area at a distance which is determined by reference to the appropriate typical layout. In urban areas, where the speed limit is 60 km/h or less, the CS-33 alone is sufficient. In rural areas, a CS-33A may be added at a distance of 1.0 km in advance of the area. For high speed roads such as freeways, additional CS-33A signs may be installed at a distance of 2.0 km or more from the approach area.