The object of this paper is to analyse the impact of merges, lane drops and incidents on capacity drops, a very important aspect for motorway operations. Traffic is assumed to be described by a LWR model, and the area subject to some capacity restriction is described by an internal state node model. This model is modified in order to accommodate the impact of the boundedness of traffic acceleration. Some specific aspects of this model (phase transition) will be analysed in depth. The dynamics of the node result from interaction of the node's supplies and demands with incoming demands and outgoing supplies. It will be shown that the model accounts for capacity drop and hysteresis phenomena; the analysis extends to the case of merges. Comparisons will be carried out between the model and data collected on the Boulevard Périphérique in Paris for traffic management and driver information.