The Not-So-Fundamental Relationship Between Traffic Flow and Speed?

Kösters, Till; Specht, Sebastian; Wessel, Jan


Abstract

The fundamental diagram of traffic congestion states that driving speed generally decreases with traffic flow, and that marginal decreases become more pronounced for higher flows. We find, however, that this seemingly fundamental relationship breaks down when only very few cars are on the road, and speed actually increases with traffic flow. To reveal this surprising finding, we use a unique large-scale real-world dataset with per-minute traffic observations from the German Autobahn, and control for confounders of the speed-flow relationship in a fixed-effects regression model. By linking our robust results to psychological research on social interaction effects in traffic, we then discuss potential reasons for this behaviour.

Keywords
speed-flow relationship; fundamental diagram of traffic congestion; traffic psychology



Publication type
Working paper

Peer reviewed
No

Publication status
Published

Year
2024

Volume
41

Title of series
Institute of Transport Economics Münster — Working Paper

Place
Münster

Language
English

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