What are 5 situations where warning signs must be used in driving?

Warning signs must be used in driving in situations such as approaching a construction zone, where reduced speed and caution are necessary. When navigating sharp curves or steep hills, these signs alert drivers to adjust their speed accordingly. Additionally, in areas with pedestrian crossings or school zones, warning signs help protect vulnerable road users. Lastly, during adverse weather conditions like fog or heavy rain, warning signs indicate the need for reduced visibility and increased caution.