Are commercially implemented adaptive cruise control systems string\n stable?

Gunter, George; Gloudemans, Derek; Stern, Raphael E.; McQuade, Sean; Bhadani, Rahul; Bunting, Matt; Monache, Maria Laura Delle; Lysecky, Roman; Seibold, Benjamin; Sprinkle, Jonathan; Piccoli, Benedetto; Work, Daniel B. · 2019 · OpenAlex-citations

DOI: 10.48550/arxiv.1905.02108

archive: archived pipeline: cataloged verified

Get this paper ↗ (DOI — opens at the source; we link to it, we don't host it)

Summary

This study investigates the string stability of commercially available adaptive cruise control (ACC) systems, addressing the critical question of whether current market vehicles amplify or dissipate small disturbances in traffic platoons. While theoretical models and simulations often suggest ACC can improve traffic flow, it remained unknown if these benefits are achievable with existing commercial implementations. String instability can lead to phantom traffic jams, where small perturbations grow as they propagate through a line of vehicles. The authors aim to determine if the ACC systems in widely available 2018 model year vehicles are string stable, thereby assessing their potential impact on traffic flow stability. To answer this, the researchers conducted field tests on seven distinct vehicle models from two manufacturers, collecting data from over 1,200 miles of driving. The experimental design involved two-vehicle car-following tests where a lead vehicle drove specific speed profiles (oscillatory, step changes, and speed dips) while the follower vehicle operated with ACC engaged. High-accuracy GPS receivers recorded position and speed data. The authors used this data to calibrate a linear second-order delay differential equation model that approximates the black-box ACC behavior. They then performed stability analysis on the calibrated models using bifurcation tools. Additionally, to validate the findings for one common vehicle model, the team conducted an eight-vehicle platoon experiment using identical ACC-equipped vehicles following an autonomous lead vehicle. The results indicate that all seven tested vehicle models possess string unstable ACC systems. The calibrated models confirmed that these systems amplify disturbances rather than dissipating them. In the eight-vehicle platoon experiment, this instability was empirically validated: an initial speed disturbance of 6 mph was amplified to a 25 mph disturbance by the time it reached the last vehicle in the platoon, causing that vehicle’s ACC system to disengage. This finding contrasts with some prior simulations suggesting moderate-sized platoons might still reduce disturbances, demonstrating that the instability is significant enough to disrupt automated following in real-world conditions. The significance of this work lies in its empirical demonstration that current commercial ACC systems are not string stable, which has implications for traffic engineering and the deployment of automated vehicles. The study suggests that without connectivity or improved control laws, widespread adoption of current ACC systems may not prevent phantom traffic jams and could potentially exacerbate traffic instability. The authors provide the largest publicly available comparative driving dataset on ACC vehicles, offering a resource for future research into improving automated driving control strategies to achieve string stability.

Provenance

The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed.

Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• lane positioning