Effects of freeway traffic homogeneity on lane changing activity: The role of dynamic speed limits

Abstract

The objective of this thesis is to understand the influence of dynamic speed limits on flow rates and lane changing activity through empirical data recorded in a highway entering Barcelona. The thesis also aims to establish a better understanding of highway homogenization across lanes due to different speed limits. To that end, data of three different days under different speed limit conditions will be examined by looking at standard traffic diagrams and using various traffic tools, such as the identification of congested states and the definition of stationary periods. The main conclusions are that variable speed limits do not modify the highway capacity, but the critical occupancy, by shifting it to significantly higher occupancy rates. This contradicts previous research and shows the misuse of dynamic speed limits for mainline metering. Additionally, lane changing activity has been proved to be extremely high during congestion. However, the analyzed data does not allow an exhaustive understanding of lane changing activity for congested conditions. For uncongested states a relation between occupancy and lane changing rates has been assessed. Finally it motivates further research in these subjects.