Percentile-controlled diffusion generates calibrated corner-case scenarios for AV safety testing

Jiaxi Liu · hf · 2026-10-09

Existing AV scenario generators can enforce behavior, adversity, or feasibility but offer little control over how extreme a generated corner case is relative to plausible futures in the same traffic context.

This work defines a scenario's adversity as its percentile in the conditional distribution of future risk given the observed history. A reference risk distribution maps each requested percentile to a physical risk target; a percentile-conditioned joint diffusion model with sampling-time risk guidance then generates multi-agent futures, with a reference-based criterion for evaluating percentile realization.

Using PET as risk surrogate on highD, the method realizes 1,422 of 1,440 requests within 0.05 percentile tolerance (98.75%), mean percentile error 0.00673 and PET-target error 0.00991 s — connecting context-relative risk specification, physical realization, and evaluation on one scale.

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