Decentralized Environmental Notification (DEN) are messages transmitted between road users in automotive technology, indicating road hazards, Road Hazard Warning
(RHW), informing drivers about road conditions, congestion and obstacles. DEN messages are received by Cooperative Intelligent Transport System, C-IST, via C2C or C2I communications
and are sent periodically by IST stations, and continue until the hazard has passed or the situation has cleared. DEN warning messages include, but are not limited to, braking from vehicles ahead, wrong-way drivers, accidents, defective cars, traffic warnings, vehicles that have disregarded traffic signs, collision warnings, hazardous roadway warnings, severe weather warnings, wet and slippery roadways, reduced visibility, and wind gusts.