Abstract
The bottle-neck considered in this paper is on two-lane carriageways of motorways and due to roadworks of short duration. This mostly means that one lane is closed and that the capacity is substantially reduced. The aim of the research is to analyse the behaviour of the traffic stream in these conditions and to find an explanation for the capacity reduction. The first research topic is whether the congestion starts along the road works when traffic is on one lane or at the merging of the streams from both lanes. Some preliminary results of the study are presented, based on extensive measurements with the mobile traffic data collection system of the Transportation Research Laboratory of Delft University of Technology.