On some experimental features of car-following behavior and how to model them

TL;DR

This study investigates car-following behavior through experiments with a 25-car platoon, revealing variability in spacing at similar speeds and proposing a model that accounts for driver insensitivity in certain conditions.

Contribution

The paper extends previous experimental analysis, uncovers new findings on traffic state variability, and introduces a car-following model that better captures human driving behavior.

Findings

Traffic states occupy a 2D region in speed-spacing space

Average platoon spacing can vary significantly at the same speed

The proposed model accurately reproduces experimental results

Abstract

We have carried out car-following experiments with a 25-car-platoon on an open road section to study the relation between a car's speed and its spacing under various traffic conditions, in the hope to resolve a controversy surrounding this fundamental relation of vehicular traffic. In this paper we extend our previous analysis of these experiments, and report new experimental findings. In particular, we reveal that the platoon length (hence the average spacing within a platoon) might be significantly different even if the average velocity of the platoon is essentially the same. The findings further demonstrate that the traffic states span a 2D region in the speed-spacing (or density) plane. The common practice of using a single speed-spacing curve to model vehicular traffic ignores the variability and imprecision of human driving and is therefore inadequate. We have proposed a car-following model based on a mechanism that in certain ranges of speed and spacing, drivers are insensitive to the changes in spacing when the velocity differences between cars are small. It was shown that the model can reproduce the experimental results well.