Empirical findings regarding lane changing activity on Barcelona B-23 freeway

Abstract

Lane changing activity is thought to play an important role in the capacity degradation in congested freeways. However, proofs of this negative impact are scarce due to the difficulties in obtaining suitable data. In this paper, the lane changing activity in a freeway accessing Barcelona is analyzed. Lane changes (LC) were video recorded in six different stretches, from where loop detector measurements are also available. Recordings were treated by using a new semi-automatic method that enabled not only reducing human processing time, but also retrieving the exact time and location of each lane change. This method has been proved to be reliable and fast. A consistent relationship between LC activity and congestion has been found. LC peaks in all analyzed sections when they become congested. This is particularly intense at the interface between congestion and free flow. An example of that is a static bottleneck, LC activity downstream from the BN peaks each time this is active. Additionally, data shows that the greater the Lane Changing Probability (LCP), the smaller the maximum observable flow, adding a proof for LC to be a key contributor to a capacity drop. Regarding the per lane behavior, the greater the inter lane speed differences, typically the greater the LCP. To obtain meaningful conclusions, it is mandatory to properly plan the data collection campaign, as at some locations the precision of the observations is limited due to the lack of spatial coverage.