FlowR2A: Learning Reward-to-Action Distribution for Multimodal Driving Planning

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Summary

FlowR2A proposes a novel method that combines dense reward supervision with dynamic proposal generation using a flow-matching decoder for multimodal driving planning, achieving state-of-the-art results on the NAVSIM benchmarks.

Multimodal driving planning faces a long-standing tension between two paradigms: scoring-based methods benefit from dense reward supervision but are confined to a fixed action vocabulary, while anchor-based methods generate proposals dynamically yet suffer from sparse supervision constrained to a single ground-truth trajectory. In this work, we propose FlowR2A, which resolves this tension by reframing simulation-based rewards from discriminative targets into generative conditions. By learning the reward-conditioned action distribution from dense trajectory-reward pairs with a flow-matching decoder, FlowR2A unifies the dense supervision of scoring-based methods with the proposal generation of anchor-based methods in a single generative model, forcing the model to internalize the correlation between an action and its outcomes in safety, progress, comfort, and rule compliance. To balance hard safety constraints against soft progress objectives, we introduce fine-grained per-timestep reward conditioning and reward noise augmentation. The generative formulation naturally supports controllable test-time sampling via reward guidance and anchored sampling, producing high-quality proposals. FlowR2A achieves state-of-the-art results on the NAVSIM v1 and v2 benchmarks, with multimodal proposals of substantially higher quality than prior methods.
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Source: https://huggingface.co/papers/2606.24231

Abstract

FlowR2A addresses the tension in multimodal driving planning by combining dense reward supervision with dynamic proposal generation through a flow-matching decoder that learns reward-conditioned action distributions.

Multimodal driving planningfaces a long-standing tension between two paradigms:scoring-based methodsbenefit from dense reward supervision but are confined to a fixed action vocabulary, whileanchor-based methodsgenerate proposals dynamically yet suffer from sparse supervision constrained to a single ground-truth trajectory. In this work, we propose FlowR2A, which resolves this tension by reframingsimulation-based rewardsfromdiscriminative targetsintogenerative conditions. By learning thereward-conditioned action distributionfromdense trajectory-reward pairswith aflow-matching decoder, FlowR2A unifies the dense supervision ofscoring-based methodswith the proposal generation ofanchor-based methodsin a single generative model, forcing the model to internalize the correlation between an action and its outcomes in safety, progress, comfort, and rule compliance. To balance hard safety constraints against soft progress objectives, we introduce fine-grained per-timestep reward conditioning and reward noise augmentation. The generative formulation naturally supports controllable test-time sampling viareward guidanceandanchored sampling, producing high-quality proposals. FlowR2A achieves state-of-the-art results on theNAVSIM v1and v2 benchmarks, with multimodal proposals of substantially higher quality than prior methods.

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