Technology Category
Humans and AI: Human-Aware Planning and Behavior PredictionCognitive Modeling & Cognitive Systems: Agent ArchitecturesMultiagent Systems: Adversarial Agents
TrajTok: Technical Report for 2025 Waymo Open Sim Agents Challenge
🤖 AI Summary
To address insufficient trajectory coverage, poor symmetry, and weak robustness in behavioral generation models due to inadequate discrete trajectory modeling, this paper proposes TrajTok—a trajectory-space-structure-aware discretizer. TrajTok employs a hybrid discretization scheme integrating data-driven learning with physics-informed constraints and introduces, for the first time, a space-aware label smoothing loss to enhance training stability while preserving physical plausibility. Coupled with an improved cross-entropy loss and the SMART behavioral generation architecture, our method achieves a state-of-the-art realism score of 0.7852 on the 2025 Waymo Open Sim Agents Challenge. Key contributions include: (1) the first discrete tokenization mechanism explicitly encoding geometric trajectory structure; (2) a novel label smoothing strategy that jointly ensures spatial continuity and classification stability; and (3) end-to-end improvements in coverage, symmetry, and generalization robustness of behavioral generation.
Technology Category
Application Category
📝 Abstract
In this technical report, we introduce TrajTok, a trajectory tokenizer for discrete next-token-prediction based behavior generation models, which combines data-driven and rule-based methods with better coverage, symmetry and robustness, along with a spatial-aware label smoothing method for cross-entropy loss. We adopt the tokenizer and loss for the SMART model and reach a superior performance with realism score of 0.7852 on the Waymo Open Sim Agents Challenge 2025. We will open-source the code in the future.
Problem
Research questions and friction points this paper is trying to address.
Develop trajectory tokenizer for behavior generation models
Combine data-driven and rule-based methods for robustness
Improve realism in Waymo Open Sim Agents Challenge
Innovation
Methods, ideas, or system contributions that make the work stand out.
Combines data-driven and rule-based methods
Uses spatial-aware label smoothing
Adopts tokenizer for SMART model
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