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Sparse autoencoders make an end-to-end driving planner's route intent readable at 98.3% accuracy

AspireAI community · arXiv
End-to-end autonomous driving models plan well but are opaque, which limits observability and trust. This work applies mechanistic interpretability to a simple single-camera end-to-end path-planning model by training Sparse Autoencoders (SAEs) on its internal activations. Unsupervised clustering of the SAE latents reveals interpretable structure aligned with route intent, vehicle speed and braking behaviour, recovering route intent with 98.3% accuracy without supervision. Paired counterfactual image edits show that specific SAE features are visually grounded and respond systematically to scene changes such as traffic-light state and stop-sign presence, and steering individual SAE latents produces predictable, monotonic changes in planner outputs including lateral displacement, curvature and braking. As a practical application the authors build a lightweight adapter trained on SAE latents that reduces trajectory selection error by 3.44%, outperforming an equivalent adapter that omits the SAE latents. The limitation is scope: the study runs on one deliberately simple monocular scorer rather than a production driving stack, and the paper is a preprint without peer review noted.
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One distance function matched sparse-autoencoder features across layers and compressed feature circuits into supernodes
Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.
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