Traffic jam ahead warning is a safety related Cooperative Intelligent Transport System (C-ITS) service that has the
aim to reduce the risk of potential accidents associated
with driving in the direction of a stationary traffic jam tail.

Traffic jams can have different causes. In particular,
traffic jams which are caused by a sudden change of
capacity on roads – for example by a broken down
vehicle or an accident – have often a stationary traffic
jam tail. When this tail is behind a curve or hill tip or
the drivers of the following vehicles are inattentive,
it can come to accidents with very serious results.

Therefore, this service should help to detect traffic jams reliably and inform upstream road users about the tail of traffic jams timely. By this way, the drivers can adapt their driving behaviour.

On the micro level, this service should improve the usage of the Adaptive Cruise Control (ACC), for example, by starting to decelerate and provide the information of appropriate interfaces (acoustic, visual or haptic) in the vehicles.