Organizations: PDL Lab, National University of Defense Technology, Hunan, China · Shandong University, Shandong, China · HKUST (GZ) · Didichuxing Co. Ltd, Beijing, China · HKUST (GZ) and HKUST
Spatio-temporal traffic data are central to intelligent transportation systems, yet their heterogeneity poses significant challenges for large-scale modeling. Existing pre-trained models often rely on a homogeneous modeling paradigm to handle highly heterogeneous traffic data. This fundamental mismatch not only limits model generalization but also leads to computationally expensive and parameter-inefficient designs. To this end, we propose FlexST, a novel pre-training framework that introduces modularity and adaptivity for traffic modeling. Specifically, we first propose a multi-resolution spatio-temporal diffusion module that captures both short-term fluctuations and long-range trends, effectively reconciling inputs with divergent temporal and spatial resolutions. After that, we construct a domain-adaptive mixture-of-experts that dynamically routes data to specialized sub-networks, enabling selective knowledge transfer while preventing negative interference across diverse domains. Moreover, we devise a unified periodic encoding strategy that injects resolution- and domain-aware inductive biases to harmonize periodic inconsistencies across datasets. Extensive experiments on 23 real-world traffic datasets demonstrate that FlexST significantly outperforms state-of-the-art baselines in zero- and few-shot settings, showcasing superior generalization, adaptability and efficiency. This work offers a new direction for building general-purpose pre-trained models capable of handling the complexity and variability of urban traffic systems.
Figures & tables
Fig. 1 : Weekly average traffic time series across regions, highlighting heterogeneity across cities (top: Hangzhou vs. Jinan), temporal resolutions (middle: Beijing Subway 10 min vs. 15 min), and variables (bottom: PEMS08 flow vs. speed). Z-score normalization handles large value differences.
Fig. 2 : The model pipeline.
Fig. 3 : Aligning different temporal resolutions by time span ensures that patches of the same absolute duration are compared consistently, regardless of their length or resolution.
Dataset
PEMS04
PEMS08
Didi-SZ
Beijing Taxi
HZMetro
CHI-Bike
Beijing Subway
Inflow
Outflow
Inflow
Outflow
Inflow
Outflow
Inflow
Outflow
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
HA
38.67
57.49
31.93
47.72
3.19
4.81
56.39
94.83
56.47
94.93
130.30
235.99
130.00
219.45
6.02
11.18
5.99
11.53
238.66
425.64
232.28
454.64
TimesFM
36.84
56.62
30.43
47.10
3.09
4.70
48.84
85.42
48.93
85.53
113.21
216.89
114.88
204.20
5.69
10.57
5.63
10.83
201.74
385.23
197.52
415.69
Timer
125.88
152.52
117.77
141.59
7.83
10.58
90.80
127.08
90.84
127.18
150.13
258.28
150.24
245.23
6.24
12.91
6.24
13.23
224.25
425.30
219.84
463.39
Sundial
36.56
55.35
30.20
46.14
3.18
4.84
50.90
88.25
51.01
88.38
123.18
221.96
124.59
221.96
5.85
10.99
5.82
11.35
224.25
425.30
219.84
463.39
TABLE I : Zero-shot performance on short-term prediction. We bold the best and underline the second models.
Dataset
PEMS04
PEMS08
Didi-SZ
HZMetro
Inflow
Outflow
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
HA
123.73
160.18
104.67
137.75
5.04
6.86
106.77
193.77
106.63
183.58
TimesFM
95.63
132.00
72.03
105.05
4.28
5.96
87.759
218.089
78.832
182.676
Timer
111.52
132.88
106.06
128.96
6.39
8.82
142.714
242.061
145.531
236.142
Sundial
101.46
136.81
67.46
97.97
4.82
6.50
159.44
313.21
157.96
304.78
TABLE II : Zero-shot performance on long-term prediction.
Dataset
PEMS08
Didi-SZ
TrafficZZ
NYC-Taxi
CHI-Taxi
NYC-Bike
CHI-Bike
Inflow
Outflow
Inflow
Outflow
Inflow
Outflow
Inflow
Outflow
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
HA
32.19
48.07
3.17
4.79
1.46
2.09
16.99
38.73
25.15
51.74
4.42
11.53
4.80
12.46
14.47
10.48
14.30
24.16
6.16
11.54
5.99
11.54
Informer
69.10
94.23
3.05
4.70
1.09
1.79
18.54
41.33
30.07
57.14
4.13
13.15
4.62
14.81
13.45
24.82
13.42
24.50
4.37
8.89
4.27
8.76
PatchTST
22.26
35.58
2.82
4.34
1.16
1.80
11.37
26.91
17.25
38.02
3.30
8.42
3.60
9.40
10.87
19.77
10.86
19.34
5.00
9.68
4.88
9.55
STGCN
28.99
42.40
3.39
5.09
1.07
1.69
17.71
38.17
28.68
52.78
3.66
11.17
4.10
13.04
11.11
21.87
11.10
21.66
3.53
7.24
3.52
7.18
TABLE III : Few-shot performance on short-term prediction using training data of 7 days.
Dataset
PEMS08
Didi-SZ
TrafficZZ
NYC-Taxi
NYC-Bike
Inflow
Outflow
Inflow
Outflow
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
MAE
RMSE
HA
105.80
139.29
4.95
6.75
1.18
1.66
13.87
31.39
20.99
42.47
11.86
20.41
11.66
20.04
Informer
87.83
118.34
3.69
5.38
1.09
1.77
19.56
43.31
31.40
59.84
13.45
24.50
13.37
24.13
PatchTST
46.88
73.00
3.35
5.07
0.59
0.95
7.31
18.71
11.45
27.58
7.44
14.28
7.68
14.55
STGCN
51.81
74.70
4.11
5.82
1.09
1.72
22.84
45.49
34.75
60.09
10.73
21.24
10.66
20.81
TABLE IV : Few-shot performance on long-term prediction using training data of 7 days.
Fig. 4 : Comparative performance evaluation of few-shot prediction with varying training data volumes (1, 3, and 7 days).
Fig. 5 : Peak memory, inference throughput and model parameter counts.
Fig. 6 : Ablation study.
Notation
Description
G=(V,A)
Graph with spatial units V and adjacency matrix A representing spatial connections
X∈RN×T
Single-domain traffic data with T observations per spatial unit n∈N , characterized by task type Q , temporal resolution R , spatial resolution D and spatial graph G
S
Time span of time series, determining its absolute duration
ts
timestamps associated with observations
D,Di
Spatial resolution and spatial receptive field at resolution i
X
Multi-domain traffic dataset
TABLE V : Summary of notations used in this paper.
Fig. 7 : Spatio-temporal dynamics observed across different forecasting tasks (left) and temporal resolutions (right).
Dataset
Traffic Flow
Taxi Demand
Traffic Speed
Metro Flow
Congestion Level
Total
# of Regions
1,957
263
2,676
564
524
3,584
# of Records
71,834,110
9,240,768
28,015,352
5,621,616
9,054,720
123,766,566
Sampling Rate
5T
30T
5T, 30T
10T, 15T
10T
5T, 10T, 15T, 30T
Source
[ 3 , 12 ]
[ 36 ]
[ 8 , 38 ]
[ 39 , 40 ]
[ 41 ]
-
TABLE VI : Statistical information of the pre-training datasets, which are aggregated based on the measured variables. For sampling rate: T=minute, H=hour. We provide detailed description of each dataset in supplementary material.
Dataset
PEMS04
PEMS08
GBA
NYC-Taxi
CHI-Taxi
Beijing Taxi
NYC-Bike
CHI-Bike
TrafficZZ
Beijing Subway
HZMetro
Didi-SZ
Task
Traffic Flow
Traffic Flow
Traffic Flow
Taxi Demand
Taxi Demand
Taxi Demand
Bicycle Sharing
Bicycle Sharing
Traffic Speed
Metro Flow
Metro Flow
Congestion Level
# of Regions
307
170
2,352
263
77
1,024
540
270
676
276
80
627
# of Records
5,216,544
3,035,520
124,637,184
46,102,848
2,698,080
43,745,280
113,633,280
2,384,640
948,428
993,600
292,000
10,834,560
Sampling Rate
5T
5T
5T
30T
30T
30T
30T
30T
30T
15T
15T
10T
Source
[ 3 ]
[ 3 ]
[ 12 ]
[ 36 ]
[ 36 ]
[ 8 ]
[ 36 ]
[ 37 ]
[ 8 ]
[ 38 ]
[ 40 ]
[ 41 ]
TABLE VII : Statistical information of the downstream evaluation datasets. Notice that, the evaluation datasets differ from the pre-training datasets in terms of spatial regions, sampling rates, tasks, or years .
Department of Computer Science and Software Engineering, Auckland University of Technology, Auckland 1010, New Zealand · Department of Data Science and Artificial Intelligence, Auckland University of Technology, Auckland 1010, New Zealand