Empirical analysis of traffic sensor data surrounding a bottleneck on a German Autobahn

The evolution of traffic from freely flowing to queued conditions and from queued to freely flowing conditions was studied along a 14-km section of German Autobahn 9 near Munich. Several bottlenecks were identified by a systematic examination of the excess vehicle accumulation and excess travel time (delay) that arose between measurement locations. It is shown that a bottleneck arose repeatedly downstream of an on-ramp on a busy freeway. The analysis tools used were curves of cumulative vehicle arrival number versus time and curves of cumulative time-averaged velocity versus time. The data required to construct these curves were available in archived form from inductive loop detectors embedded in the freeway. These cumulative plots were carefully and systematically transformed to produce the resolution necessary to reveal important details of the evolution of traffic flow features. These high-resolution transformed curves have made it possible to identify key time-dependent features related to the activation and deactivation of the bottleneck.