Capacity bottlenecks in the road network limit the capacity of the adjacent sections. A frequent cause for such capacity bottlenecks in the major road network are lane drop offs in the context of construction sites. On Austrian motorway, construction site caused by capacity bottlenecks are concentrated to the summer, when the traffic volume rises by reasons of holiday traffic, in addition to the common level. These arrays are designed as merging segments, where vehicles change from the off dropping to the remaining lanes. These manoeuvres cause discontinuity in the traffic flow, so that the capacity of a merging section is lower than the one of a basic freeway lane.

Experiences show, traffic overloads cause unstable conditions of the traffic flow, which reduce the capacity clearly and also result in a decrease of traffic safety; suitable traffic management and information measures can increase the capacity; compliance suffers from discrepancies between posted information and actual traffic situation.