Abstract

TRB 2014 - Transportation Research Board 93rd Annual Meeting, WASHINGTON D.C, ETATS-UNIS, 12-/01/2014 - 16/01/2014; An empirical analysis is conducted on lane changing behavior using a trajectory data set collected at a weaving section in Grenoble (France). A detailed literature review shows that strong empirical understanding of the weaving mechanisms is still lacking. The goal is to investigate the lane changing behavior at a microscopic level. Data collection distinguished lane changes from the main road and those towards the main road. Descriptive empirical analysis examines the positions of the lane changes and the corresponding accepted gaps. Results show that under heavy congested traffic conditions the weaving vehicles tend to change lane as soon as possible after the start of the weaving section. When the traffic conditions are fluid, the weaving vehicles coming from the main road tend to change lane earlier than the weaving vehicles coming from the auxiliary lane. Moreover, weaving vehicles coming from the auxiliary lane accept smaller gaps and headways than the weaving vehicles coming from the main road. Our findings are questioning some results of previous works using micro-simulation to study weaving sections. As the weaving vehicles change lane at the beginning of the studied weaving section, our findings ask whether the length of the weaving section is a key variable to estimate its capacity. Our findings raise also some questions about the relevance of the gap acceptance theory to model lane changes at weaving sections. But further research are needed to asses these hypothesis.

Abstract

This paper presents the Dynamic Speed Limit (DSL) experiment that took place in June 2013 on the last 13 km stretch of the B-23 freeway accessing the city of Barcelona (Spain). The DSL system installed on that freeway in addition to the high density of surveillance equipment available makes this stretch a suitable highway lab. The objective of the experiment was to construct a comprehensive database of traffic engineering variables on a freeway site when different speed limits apply. Special attention was paid to ensure similar demand conditions between different scenarios. The experiment included the modification of the speed limits on a freeway segment making use of dynamic signals. Detailed measurements of vehicle counts, speeds, occupancies, lane changing maneuvers and travel times were taken. These simultaneous measurements obtained from very different types of monitoring equipment have been grouped into a single database. These include measurements from inductive loop detectors, radar, ultrasound and passive infrared non-intrusive traffic detectors, TV cameras and license plate recognition devices. The potential of this multi-source database is huge. For instance, a preliminary analysis empirically proves that drivers’ compliance with dynamic speed limits is very limited, unless speed enforcement devices are present. In addition, it is also proved that lane changing rates increase together with the occupancy level of the freeway. This comprehensive DSL database, unique in its nature, is made publicly available to the whole research community [Link], [1] in order to use up all its information. The present paper aims to present in detail this DSL experiment and its preliminary results and to contribute in the dissemination of the resulting database. This will facilitate its analysis to any interested researcher, and would lead to a better understanding of the causes and effects of DSL strategies on freeways.