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GTR: A General, Multi-View, and Dynamic Framework for Trajectory Representation Learning
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Proposes GTR, a pre-train/fine-tune trajectory representation framework that fuses free-space and road-network views, uses a spatio-temporal mixture-of-experts, and updates online by freezing lower Transformer layers.
Problem
Existing trajectory representation learning methods use only a single view (free-space or road network), rely on task-specific training, and do not support online model updates as trajectory data streams in.
Approach
Combines a multi-view encoder (GAT road embeddings, grid+POI embeddings, position and multi-granularity time embeddings), a spatio-temporal MoE that dynamically weights spatial and temporal experts per task, span-masking MLM plus VAE-based hard-negative triplet pre-training, and an online frozen-hot update that freezes the first half of Transformer layers.
Key results
- On Porto travel time estimation, GTR reaches MAE 0.01512 vs. 0.37485 for the best baseline START.
- Top-k similarity search on Beijing: GTR HR@1 0.9906 and MR 1.0130 versus 0.9720 HR@1 for the best baseline JGRM.
- Trajectory imputation on Porto: GTR Recall@3 0.86465 vs. 0.68170 for MTrajRec.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| add time embedding (ablation) | GTR · Beijing | HR@1: 0.9750 -> 0.9906 | Helped |
| add grid embedding and grid POI features (ablation) | GTR · Beijing | HR@1: 0.9810 -> 0.9906 | Helped |
| use GAT road embedding instead of replacing it with embedding vectors (ablation) | GTR · Beijing | HR@1: 0.9880 -> 0.9906 | Helped |
| add ST-MoE for spatio-temporal feature fusion (ablation) | GTR · Beijing | HR@1: 0.9882 -> 0.9906 | Helped |
| add triplet pre-training loss (ablation) | GTR · Beijing | HR@1: 0.9798 -> 0.9906 | Helped |
| add MLM pre-training loss (ablation) | GTR · Beijing | HR@1: 0.0786 -> 0.9906 | Helped |
| online frozen-hot updating | GTR · Porto | MAE: 0.01512 -> 0.01947 | Hurt |
| online frozen-hot updating | GTR · Porto | ACC: 0.83213 -> 0.83904 | Helped |
Surprising findings
- Removing the MLM loss causes Porto MR to jump from about 1 to 741, indicating the MLM pre-training is critical for similarity search.
- GTR's training time (179.6 min) is the longest among compared models, exceeding START and JGRM.
Limitations
- Training time is substantially higher than most baselines (179.6 min vs. 5-119 min).
- Evaluated only on two city datasets (Porto and Beijing) in the main experiments, with one extra Chengdu similarity experiment.
- Online updating is evaluated with a single-epoch simulation on the validation set rather than a true streaming deployment.
Experimental setup
Datasets: Porto Beijing
Benchmarks: Porto Beijing
Metrics: MR HR@1 HR@5 MAE MSE MAPE Recall@3 Recall@5 MAP ACC
Baselines: Trembr PIM Toast START LightPath JGRM TS-TrajGen SeqGAN Trajbert Bi-STDDP EB-OTS S3
Builds on: START Trembr Toast JGRM BERT
Closest papers by meaning
- TrajMamba: An Efficient and Semantic-rich Vehicle Trajectory Pre-training Model (NeurIPS 2025 · similarity 0.87)
- PLMTrajRec: A Scalable and Generalizable Trajectory Recovery Method with Pre-trained Language Models (NeurIPS 2025 · similarity 0.87)
- Holistic Semantic Representation for Navigational Trajectory Generation (AAAI 2025 · similarity 0.86)
- Towards Generalizable Trajectory Prediction using Dual-Level Representation Learning and Adaptive Prompting (CVPR 2025 · similarity 0.86)
- UniTR: A Unified Framework for Joint Representation Learning of Trajectories and Road Networks (AAAI 2025 · similarity 0.86)
- GTR-Bench: Evaluating Geo-Temporal Reasoning in Vision-Language Models (ICLR 2026 · similarity 0.86)
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