SpanVLASpanVLA

Learning from Negative-Recovery Samples with Fast Action Bridging for Vision-Language-Action Model

Zewei Zhou1,2*, Ruining Yang2,3*, Tony (Xuewei) Qi2†, Yiluan Guo2, Sherry X. Chen2,
Tao Feng2, Kateryna Pistunova2, Yishan Shen2, Lili Su3, Jiaqi Ma1
1 University of California, Los Angeles, USA
2 Motional, USA
3 Northeastern University, USA
*Equal contribution. †Corresponding author.
Negative and recovery driving examples before and after NR-RFT, with nuReasoning-NR benchmark results and dataset statistics
Real-world experience teaches both avoidance and correction. With NR supervision, SpanVLA predicts an earlier merge before a construction-zone lane closure and a return to the original lane after passing an obstructing truck.

Overview

Beyond positive demonstrations

Expert demonstrations teach a driving VLA what to do. Negative and recovery experiences add two complementary lessons: which behaviors to avoid, and how to correct behavior from difficult driving states.

01 / Data

nuReasoning-NR

A real-world driving dataset and benchmark combining positive reasoning, suboptimal trajectories, and expert recovery trajectories.

02 / Learning

NR-RFT

Asymmetric rewards penalize undesirable behaviors and reinforce expert corrections. Advantage correction maintains useful learning signals in difficult rollout groups.

03 / Efficiency

Efficient Action Bridge

Autoregressive reasoning guides a lightweight flow-matching expert through sparse-layer KV caches and historical trajectory initialization.

Read the abstract

Vision-Language-Action (VLA) models bring rich world knowledge and reasoning capabilities to autonomous driving. However, most driving VLAs are trained only on positive expert demonstrations, which teach models what to do but provide limited supervision on which behaviors to avoid and how to recover from these failures, leading to limited robustness. We introduce SpanVLA, a robust and efficient driving VLA, together with nuReasoning-NR, the first real-world driving dataset and benchmark for learning from negative and recovery samples. An extension of nuReasoning, it comprises 36K reasoning-intensive driving scenarios, including 3K suboptimal trajectories and 3K expert recovery trajectories. To exploit their asymmetric supervision, we introduce Negative–Recovery Reinforcement Fine-Tuning (NR-RFT), which penalizes undesirable behaviors and rewards expert corrective actions. Because challenging scenarios produce rollout groups dominated by similar suboptimal or even infeasible trajectories, it further incorporates an advantage correction to preserve informative optimization signals and encourage exploration. For efficient action generation, SpanVLA retains autoregressive reasoning and introduces a lightweight flow-matching action bridge conditioned on sparse-layer KV caches and initialized from the historical trajectory. Extensive experiments on NAVSIM v1/v2, nuReasoning, and the nuReasoning-NR benchmark demonstrate strong and robust planning performance and efficient action generation. Qualitative results across diverse challenging scenarios further highlight its planning robustness and recovery capability. The dataset and benchmark code will be released to support future research.

Real-world data & evaluation

nuReasoning-NR Dataset and Benchmark

An extension of nuReasoning with 36K interaction-intensive driving samples.

30K

Positive reasoning samples

Expert trajectories and reasoning annotations teach decision-making and planning.

3K

Negative samples

Suboptimal trajectories show
which behaviors to avoid.

3K

Expert recovery samples

Subsequent expert corrections teach how to recover from challenging driving states.

Negative sample showing suboptimal hesitation behind a leading vehicle, and recovery sample showing an aborted merge followed by correction to the nearest lane

Learning from experience

Negative–Recovery Reinforcement Fine-Tuning

Penalize negative behavior

Penalize matching negative behavior.
Beyond the matching threshold,
no extra reward is given.

Reward expert recovery

Agreement with an expert correction earns a recovery reward, alongside the driving-quality reward.

Correct difficult advantages

Remove standard-deviation normalization.
Use a virtual reward for all-zero groups
to preserve learning signals.

SpanVLA framework combining supervised fine-tuning, negative-recovery reinforcement fine-tuning, and a flow-matching action bridge
SpanVLA framework. SFT aligns reasoning and planning; NR-RFT uses negative penalties, recovery rewards, and corrected group-relative advantages. At inference, the VLM delegates continuous trajectory generation to the action bridge.

Efficient inference

Efficient action bridging for fast action generation

Sparse VLM KV caches condition a cross-attention flow-matching action bridge initialized from historical motion

Sparse-layer KV conditioning

Accessing selected VLM layers provides multi-granular context with less computation than dense layer-wise conditioning.

Historical trajectory initialization

Flow matching learns the transformation from past motion to future actions, using historical trajectory embeddings as its starting point.

Experimental evidence

Better avoidance. Stronger recovery.

nuReasoning-NR benchmark · 300 negative + 300 recovery scenarios
Method / supervisionNegative ↑Recovery ↑Average PDMS ↑
LTF · positive only62.751.056.8
ReCogDrive · positive only64.054.059.0
AutoVLA · positive only64.254.059.1
SpanVLA · positive only65.156.160.6
AutoVLA + NR68.859.564.2
SpanVLA + NR74.165.169.6 (+14.9%)

Negative-Sample Results

Original animated negative-sample demonstration comparing planning before and after reinforcement fine-tuning

Recovery-Sample Results

Original animated recovery-sample demonstration comparing planning before and after reinforcement fine-tuning

Planning performance across benchmarks

NAVSIM results · navtest and navhard
MethodSensorsNAVSIM v1
PDMS ↑
NAVSIM v2
EPDMS ↑
v2 navhard
EPDMS ↑
TransFuserCamera + LiDAR84.076.723.1
Hydra-MDPCamera + LiDAR86.581.4—
DiffusionDriveCamera + LiDAR88.184.524.2
AutoVLACamera89.182.4—
ReCogDriveCamera89.683.6—
DriveVLA-W0Camera90.286.1—
Qwen-DriveCamera90.7——
RAP-DINO———36.9
SpanVLACamera90.886.940.8
SpanVLA* · best-of-6Camera93.390.547.9

Fast action generation at higher trajectory resolution

Action generation efficiency · NAVSIM v1
MethodWaypointsTrajectory generation ↓Total latency ↓
AutoVLA · autoregressive100.40 s1.25 s
SpanVLA · flow matching100.08 s0.67 s
AutoVLA · autoregressive501.72 s2.57 s
SpanVLA · flow matching500.08 s0.67 s

For 50-waypoint trajectories, action generation takes 0.08 s instead of 1.72 s (21.5× faster). Reported total latency falls from 2.57 s to 0.67 s (approximately 74% lower). The bridge’s measured trajectory-generation time stays approximately unchanged from 10 to 50 waypoints.

Resources

Citation

BibTeX · updated manuscript title
@article{zhou2026spanvla,
  author  = {Zhou, Zewei and Yang, Ruining and Qi, Xuewei and Guo, Yiluan and Chen, Sherry X. and Feng, Tao and Pistunova, Kateryna and Shen, Yishan and Su, Lili and Ma, Jiaqi},
  title   = {SpanVLA: Learning from Negative-Recovery Samples with Fast Action Bridging for Vision-Language-Action Model},
  journal = {arXiv preprint arXiv:2604.19710},
  year    = {2026}
}

Acknowledgements

We thank Qian Zhu, Haram Kim, and Baoshu Qi for data preparation and annotation of nuReasoning-NR; Muhammad Taufik Tirtosudiro and Jiong Yang for support with the evaluation pipeline; and Nitin Kapania, Sourabh Vora, and Balajee Kannan for their support for the project. We also thank the Amazon AI PhD Fellowship and the Qualcomm Innovation Fellowship for their support.