On interchanges there are higher probabilities of risky situations compared to uninterrupted motorway sections due to increased speed variability and higher frequency of lane-changes. In this study, we focus on understanding and modelling drivers’ longitudinal speed behavior when negotiating horizontal ramp curves in interchanges in the Netherlands. For this purpose, detailed trajectory data of free-moving vehicles on 29 different curves from 6 different interchanges were collected from video images taken from a hovering helicopter. Only free-moving vehicles were chosen in order to understand how the road geometric design affects the (unhindered) driving speeds. The results of the speed profiles analysis show that for each connection, the speed profiles follow certain patterns, despite the large heterogeneity among drivers. These speed patterns were found to be significantly affected by the distance along a connection, the design characteristics of a connection, vehicle type, and drivers’ heterogeneity. The impact of the distance along the connection on the speed was found to be significant and non-linear. This indicates that drivers do not maintain constant speeds, but adapt it along the connections. These models, which describe drivers’ speed behavior and adaptation along different connections, are useful for improving current speed behavior models used in different microscopic simulation packages, and provide designers with a tool to estimate the speeds during the design process. The insights from this study, and the identified models, are also useful for enhancing the acceptability of automated vehicles’ longitudinal behavior by adapting it to human like behavior.
Bibliographical noteAccepted Author Manuscript
- Horizontal curves
- Speed behavior
- Trajectory data