Ruiping Liu 0001

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20ranked-venue papers
3as first author
20since 2021 · last 2026
0000-0001-5245-2277ORCID · conflict

Domains — the database's venue-derived domains; a paper can count in several

Artificial intelligence and machine learning · 14 · 2 first-author · 14 since 2021Graphics, computer vision, multimedia, augmented reality and games · 10 · 10 since 2021Applied, interdisciplinary, general and emerging computing · 4 · 1 first-author · 4 since 2021Human-computer interaction and ubiquitous computing · 2 · 2 since 2021Systems, architecture and hardware · 1 · 1 since 2021
YearPublicationVenuePosition
2026 HybriDLA: Hybrid Generation for Document Layout Analysis
abstract
Conventional document layout analysis (DLA) traditionally depends on empirical priors or a fixed set of learnable queries executed in a single forward pass. While sufficient for early-generation documents with a small, predetermined number of regions, this paradigm struggles with contemporary documents, which exhibit diverse element counts and increasingly complex layouts. To address challenges posed by modern documents, we present HybriDLA, a novel generative framework that unifies diffusion and autoregressive decoding within a single layer. The diffusion component iteratively refines bounding-box hypotheses, whereas the autoregressive component injects semantic and contextual awareness, enabling precise region prediction even in highly varied layouts. To further enhance detection quality, we design a multi-scale feature-fusion encoder that captures both fine-grained and high-level visual cues. This architecture elevates performance to 83.5% mean Average Precision (mAP). Extensive experiments on the DocLayNet and M6Doc benchmarks demonstrate that HybriDLA sets a state-of-the-art performance, outperforming previous approaches.
Yufan Chen 0001, Omar Moured, Ruiping Liu 0001, Junwei Zheng, Kunyu Peng, Jiaming Zhang 0001, Rainer Stiefelhagen
AAAI3
2025 Scene-agnostic Pose Regression for Visual Localization
abstract
Absolute Pose Regression (APR) predicts 6D camera poses but lacks the adaptability to unknown environments without retraining, while Relative Pose Regression (RPR) generalizes better yet requires a large image retrieval database. Visual Odometry (VO) generalizes well in unseen environments but suffers from accumulated error in open trajectories. To address this dilemma, we introduce a new task, Scene-agnostic Pose Regression (SPR), which can achieve accurate pose regression in a flexible way while eliminating the need for retraining or databases. To benchmark SPR, we created a large-scale dataset, 360SPR, with over 200K photorealistic panoramas, 3.6M pinhole images and camera poses in 270 scenes at three different sensor heights. Furthermore, a SPR-Mamba model is initially proposed to address SPR in a dual-branch manner. Extensive experiments and studies demonstrate the effectiveness of our SPR paradigm, dataset, and model. In the unknown scenes of both 360SPR and 360Loc datasets, our method consistently outperforms APR, RPR and VO. The dataset and code are available at SPR.
Junwei Zheng, Ruiping Liu 0001, Yufan Chen 0001, Zhenfang Chen, Kailun Yang 0001, Jiaming Zhang 0001, Rainer Stiefelhagen
CVPR2
2025 Graph-based Document Structure Analysis
abstract
When reading a document, glancing at the spatial layout of a document is an initial step to understand it roughly. Traditional document layout analysis (DLA) methods, however, offer only a superficial parsing of documents, focusing on basic instance detection and often failing to capture the nuanced spatial and logical relationships between instances. These limitations hinder DLA-based models from achieving a gradually deeper comprehension akin to human reading. In this work, we propose a novel graph-based Document Structure Analysis (gDSA) task. This task requires that model not only detects document elements but also generates spatial and logical relations in form of a graph structure, allowing to understand documents in a holistic and intuitive manner. For this new task, we construct a relation graph-based document structure analysis dataset(GraphDoc) with 80K document images and 4.13M relation annotations, enabling training models to complete multiple tasks like reading order, hierarchical structures analysis, and complex inter-element relationship inference. Furthermore, a document relation graph generator (DRGG) is proposed to address the gDSA task, which achieves performance with 57.6% at $mAP_g$@$0.5$ for a strong benchmark baseline on this novel task and dataset. We hope this graphical representation of document structure can mark an innovative advancement in document structure analysis and understanding. The new dataset and code will be made publicly available.
Yufan Chen 0001, Ruiping Liu 0001, Junwei Zheng, Di Wen 0006, Kunyu Peng, Jiaming Zhang 0001, Rainer Stiefelhagen
ICLR2
2025 Exploring Self-supervised Skeleton-based Action Recognition in Occluded Environments
abstract
To integrate action recognition into autonomous robotic systems, it is essential to address challenges such as person occlusions—a common yet often overlooked scenario in existing self-supervised skeleton-based action recognition methods. In this work, we propose IosPSTL, a simple and effective self-supervised learning framework designed to handle occlusions. IosPSTL combines a cluster-agnostic KNN imputer with an Occluded Partial Spatio-Temporal Learning (OPSTL) strategy. First, we pre-train the model on occluded skeleton sequences. Then, we introduce a cluster-agnostic KNN imputer that performs semantic grouping using k-means clustering on sequence embeddings. It imputes missing skeleton data by applying K-Nearest Neighbors in the latent space, leveraging nearby sample representations to restore occluded joints. This imputation generates more complete skeleton sequences, which significantly benefits downstream self-supervised models. To further enhance learning, the OPSTL module incorporates Adaptive Spatial Masking (ASM) to make better use of intact, high-quality skeleton sequences during training. Our method achieves state-of-the-art performance on the occluded versions of the NTU-60 and NTU-120 datasets, demonstrating its robustness and effectiveness under challenging conditions. Code is available at https://github.com/cyfml/OPSTL.
Kunyu Peng, Alina Roitberg, David Schneider 0006, Jiaming Zhang 0001, Junwei Zheng, Yufan Chen 0001, Ruiping Liu 0001, Kailun Yang 0001, Rainer Stiefelhagen
IJCNN8
2025 Situat3DChange: Situated 3D Change Understanding Dataset for Multimodal Large Language Model
abstract
Physical environments and circumstances are fundamentally dynamic, yet current 3D datasets and evaluation benchmarks tend to concentrate on either dynamic scenarios or dynamic situations in isolation, resulting in incomplete comprehension. To overcome these constraints, we introduce Situat3DChange, an extensive dataset supporting three situation-aware change understanding tasks following the perception-action model: 121K question-answer pairs, 36K change descriptions for perception tasks, and 17K rearrangement instructions for the action task. To construct this large-scale dataset, Situat3DChange leverages 11K human observations of environmental changes to establish shared mental models and shared situational awareness for human-AI collaboration. These observations, enriched with egocentric and allocentric perspectives as well as categorical and coordinate spatial relations, are integrated using an LLM to support understanding of situated changes. To address the challenge of comparing pairs of point clouds from the same scene with minor changes, we propose SCReasoner, an efficient 3D MLLM approach that enables effective point cloud comparison with minimal parameter overhead and no additional tokens required for the language decoder. Comprehensive evaluation on Situat3DChange tasks highlights both the progress and limitations of MLLMs in dynamic scene and situation understanding. Additional experiments on data scaling and cross-domain transfer demonstrate the task-agnostic effectiveness of using Situat3DChange as a training dataset for MLLMs. The established dataset and source code are publicly available at: https://github.com/RuipingL/Situat3DChange.
Ruiping Liu 0001, Junwei Zheng, Yufan Chen 0001, Kunyu Peng, Kailun Yang 0001, Jiaming Zhang 0001, Marc Pollefeys, Rainer Stiefelhagen
NeurIPS1
2025 mmWalk: Towards Multi-modal Multi-view Walking Assistance
abstract
Walking assistance in extreme or complex environments remains a significant challenge for people with blindness or low vision (BLV), largely due to the lack of a holistic scene understanding. Motivated by the real-world needs of the BLV community, we build mmWalk, a simulated multi-modal dataset that integrates multi-view sensor and accessibility-oriented features for outdoor safe navigation. Our dataset comprises $120$ manually controlled, scenario-categorized walking trajectories with $62k$ synchronized frames. It contains over $559k$ panoramic images across RGB, depth, and semantic modalities. Furthermore, to emphasize real-world relevance, each trajectory involves outdoor corner cases and accessibility-specific landmarks for BLV users. Additionally, we generate mmWalkVQA, a VQA benchmark with over $69k$ visual question-answer triplets across $9$ categories tailored for safe and informed walking assistance. We evaluate state-of-the-art Vision-Language Models (VLMs) using zero- and few-shot settings and found they struggle with our risk assessment and navigational tasks. We validate our mmWalk-finetuned model on real-world datasets and show the effectiveness of our dataset for advancing multi-modal walking assistance.
Kedi Ying, Ruiping Liu 0001, Chongyan Chen, Mingzhe Tao, Hao Shi 0004, Kailun Yang 0001, Jiaming Zhang 0001, Rainer Stiefelhagen
NeurIPS2
2025 Exploring Video-Based Driver Activity Recognition under Noisy Labels
abstract
As an open research topic in the field of deep learning, learning with noisy labels has attracted much attention and grown rapidly over the past ten years. Learning with label noise is crucial for driver distraction behavior recognition, as real-world video data often contains mislabeled samples, impacting model reliability and performance. However, label noise learning is barely explored in the driver activity recognition field. In this paper, we propose the first label noise learning approach for the driver activity recognition task. Based on the cluster assumption, we initially enable the model to learn clustering-friendly low-dimensional representations from given videos and assign the resultant embeddings into clusters. We subsequently perform co-refinement within each cluster to smooth the classifier outputs. Furthermore, we propose a flexible sample selection strategy that combines two selection criteria without relying on any hyperparameters to filter clean samples from the training dataset. We also incorporate a self-adaptive parameter into the sample selection process to enforce balancing across classes. A comprehensive variety of experiments on the public Drive&Act dataset for all granularity levels demonstrates the superior performance of our method in comparison with other label-denoising methods derived from the image classification field. The source code is available at https://github.com/ilonafan/DAR-noisy-labels.
Linjuan Fan, Di Wen 0006, Kunyu Peng, Kailun Yang 0001, Jiaming Zhang 0001, Ruiping Liu 0001, Yufan Chen 0001, Junwei Zheng, Rainer Stiefelhagen
SMC6
2025 Snap, Segment, Deploy: A Visual Data and Detection Pipeline for Wearable Industrial Assistants
abstract
Industrial assembly requires rapid adaptation to complex procedures under constrained computing, connectivity, and privacy conditions, rendering cloud-based solutions impractical. We present an on-device assistant for real-time, semi-hands-free guidance, integrating lightweight detection, speech recognition, and retrieval-augmented response generation. To enable scalable training without manual labeling, we construct the Gear8 dataset via an automated pipeline and introduce a two-stage refinement strategy to enhance robustness against domain shift. Experiments show improved generalization under diverse corruptions. User studies confirm notable gains in efficiency and error reduction, underscoring the system’s suitability for real-world industrial deployment. The Gear8 dataset, models, and code are publicly available at: https://github.com/Kratos-Wen/Gear8.
Di Wen 0006, Junwei Zheng, Ruiping Liu 0001, Kunyu Peng, Rainer Stiefelhagen
SMC3
2025 @BENCH: Benchmarking Vision-Language Models for Human-centered Assistive Technology
abstract
As Vision-Language Models (VLMs) advance, human-centered Assistive Technologies (ATs) for helping People with Visual Impairments (PVIs) are evolving into generalists, capable of performing multiple tasks simultaneously. However, benchmarking VLMs for ATs remains under-explored. To bridge this gap, we first create a novel AT benchmark (@ Bench). Guided by a pre-design user study with PVIs, our benchmark includes the five most crucial vision-language tasks: Panoptic Segmentation, Depth Estimation, Optical Character Recognition (OCR), Image Captioning, and Visual Question Answering (VQA). Besides, we propose a novel AT model (@MODEL) that addresses all tasks simultaneously and can be expanded to more assistive functions for helping PVIs. Our framework exhibits outstanding performance across tasks by integrating multi-modal information, and it offers PVIs a more comprehensive assistance. Extensive experiments prove the effectiveness and generalizability of our framework.
Junwei Zheng, Ruiping Liu 0001, Jiaming Zhang 0001, Sven Matthiesen, Rainer Stiefelhagen
WACV3
2024 Navigating Open Set Scenarios for Skeleton-Based Action Recognition
abstract
In real-world scenarios, human actions often fall outside the distribution of training data, making it crucial for models to recognize known actions and reject unknown ones. However, using pure skeleton data in such open-set conditions poses challenges due to the lack of visual background cues and the distinct sparse structure of body pose sequences. In this paper, we tackle the unexplored Open-Set Skeleton-based Action Recognition (OS-SAR) task and formalize the benchmark on three skeleton-based datasets. We assess the performance of seven established open-set approaches on our task and identify their limits and critical generalization issues when dealing with skeleton information.To address these challenges, we propose a distance-based cross-modality ensemble method that leverages the cross-modal alignment of skeleton joints, bones, and velocities to achieve superior open-set recognition performance. We refer to the key idea as CrossMax - an approach that utilizes a novel cross-modality mean max discrepancy suppression mechanism to align latent spaces during training and a cross-modality distance-based logits refinement method during testing. CrossMax outperforms existing approaches and consistently yields state-of-the-art results across all datasets and backbones. We will release the benchmark, code, and models to the community.
Kunyu Peng, Junwei Zheng, Ruiping Liu 0001, David Schneider 0006, Jiaming Zhang 0001, Kailun Yang 0001, M. Saquib Sarfraz, Rainer Stiefelhagen, Alina Roitberg
AAAI4
2024 OneBEV: Using One Panoramic Image for Bird's-Eye-View Semantic Mapping
Jiale Wei, Junwei Zheng, Ruiping Liu 0001, Jie Hu 0039, Jiaming Zhang 0001, Rainer Stiefelhagen
ACCV (10)3
2024 RoDLA: Benchmarking the Robustness of Document Layout Analysis Models
abstract
Before developing a Document Layout Analysis (DLA) model in real-world applications, conducting comprehensive robustness testing is essential. However, the robustness of DLA models remains underexplored in the literature. To address this, we are the first to introduce a robustness benchmark for DLA models, which includes 450K document images of three datasets. To cover realistic corruptions, we propose a perturbation taxonomy with 12 common document perturbations with 3 severity levels inspired by realworld document processing. Additionally, to better understand document perturbation impacts, we propose two metrics, Mean Perturbation Effect (mPE) for perturbation assessment and Mean Robustness Degradation (mRD) for robustness evaluation. Furthermore, we introduce a self-titled model, i.e., Robust Document Layout Analyzer (RoDLA), which improves attention mechanisms to boost extraction of robust features. Experiments on the proposed benchmarks (PubLayNet-P, DocLayNet-P, andM6Doc-P) demonstrate that RoDLA obtains state-of-the-art mRD scores of 115.7, 135.4, and 150.4, respectively. Compared to previous methods, RoDLA achieves notable improvements in mAP of +3.8%, +7.1% and +12.1%, respectively.
Yufan Chen 0001, Jiaming Zhang 0001, Kunyu Peng, Junwei Zheng, Ruiping Liu 0001, Philip Torr 0001, Rainer Stiefelhagen
CVPR5
2024 Referring Atomic Video Action Recognition
Kunyu Peng, Jia Fu 0001, Kailun Yang 0001, Di Wen 0006, Yufan Chen 0001, Ruiping Liu 0001, Junwei Zheng, Jiaming Zhang 0001, M. Saquib Sarfraz, Rainer Stiefelhagen, Alina Roitberg
ECCV (19)6
2024 Open Panoramic Segmentation
Junwei Zheng, Ruiping Liu 0001, Yufan Chen 0001, Kunyu Peng, Chengzhi Wu, Kailun Yang 0001, Jiaming Zhang 0001, Rainer Stiefelhagen
ECCV (39)2
2024 Elevating Skeleton-Based Action Recognition with Efficient Multi-Modality Self-Supervision
abstract
Self-supervised representation learning for human action recognition has developed rapidly in recent years. Most of the existing works are based on skeleton data while using a multi-modality setup. These works overlooked the differences in performance among modalities, which led to the propagation of erroneous knowledge between modalities while only three fundamental modalities, i.e., joints, bones, and motions are used, hence no additional modalities are explored.In this work, we first propose an Implicit Knowledge Exchange Module (IKEM) which alleviates the propagation of erroneous knowledge between low-performance modalities. Then, we further propose three new modalities to enrich the complementary information between modalities. Finally, to maintain efficiency when introducing new modalities, we propose a novel teacher-student framework to distill the knowledge from the secondary modalities into the mandatory modalities considering the relationship constrained by anchors, positives, and negatives, named relational cross-modality knowledge distillation. The experimental results demonstrate the effectiveness of our approach, unlocking the efficient use of skeleton-based multi-modality data. Source code will be made publicly available at https://github.com/desehuileng0o0/IKEM.
Yiping Wei, Kunyu Peng, Alina Roitberg, Jiaming Zhang 0001, Junwei Zheng, Ruiping Liu 0001, Yufan Chen 0001, Kailun Yang 0001, Rainer Stiefelhagen
ICASSP6
2024 Skeleton-Based Human Action Recognition with Noisy Labels
abstract
Understanding human actions from body poses is critical for assistive robots sharing space with humans in order to make informed and safe decisions about the next interaction. However, precise temporal localization and annotation of activity sequences is time-consuming and the resulting labels are often noisy. If not effectively addressed, label noise negatively affects the model’s training, resulting in lower recognition quality. Despite its importance, addressing label noise for skeleton-based action recognition has been overlooked so far. In this study, we bridge this gap by implementing a framework that augments well-established skeleton-based human action recognition methods with label-denoising strategies from various research areas to serve as the initial benchmark. Observations reveal that these baselines yield only marginal performance when dealing with sparse skeleton data. Consequently, we introduce a novel methodology, NoiseEraSAR, which integrates global sample selection, co-teaching, and Cross-Modal Mixture-of-Experts (CM-MOE) strategies, aimed at mitigating the adverse impacts of label noise. Our proposed approach demonstrates better performance on the established benchmark, setting new state-of-the-art standards. The source code for this study will be made accessible at https://github.com/xuyizdby/NoiseEraSAR.
Kunyu Peng, Di Wen 0006, Ruiping Liu 0001, Junwei Zheng, Yufan Chen 0001, Jiaming Zhang 0001, Alina Roitberg, Kailun Yang 0001, Rainer Stiefelhagen
IROS4
2024 Fourier Prompt Tuning for Modality-Incomplete Scene Segmentation
abstract
Integrating information from multiple modalities enhances the robustness of scene perception systems in autonomous vehicles, providing a more comprehensive and reliable sensory framework. However, the modality incompleteness in multi-modal segmentation remains under-explored. In this work, we establish a task called Modality-Incomplete Scene Segmentation (MISS), which encompasses both system-level modality absence and sensor-level modality errors. To avoid the predominant modality reliance in multi-modal fusion, we introduce a Missing-aware Modal Switch (MMS) strategy to proactively manage missing modalities during training. Utilizing bit-level batch-wise sampling enhances the model’s performance in both complete and incomplete testing scenarios. Furthermore, we introduce the Fourier Prompt Tuning (FPT) method to incorporate representative spectral information into a limited number of learnable prompts that maintain robustness against all MISS scenarios. Akin to fine-tuning effects but with fewer tunable parameters (1.1%). Extensive experiments prove the efficacy of our proposed approach, showcasing an improvement of 5.84% mIoU over the prior state-of-the-art parameter-efficient methods in modality missing. The source code is publicly available at https://github.com/RuipingL/MISS.
Ruiping Liu 0001, Jiaming Zhang 0001, Kunyu Peng, Yufan Chen 0001, Junwei Zheng, M. Saquib Sarfraz, Kailun Yang 0001, Rainer Stiefelhagen
IV1
2024 TransKD: Transformer Knowledge Distillation for Efficient Semantic Segmentation
abstract
Semantic segmentation benchmarks in the realm of autonomous driving are dominated by large pre-trained transformers, yet their widespread adoption is impeded by substantial computational costs and prolonged training durations. To lift this constraint, we look at efficient semantic segmentation from a perspective of comprehensive knowledge distillation and aim to bridge the gap between multi-source knowledge extractions and transformer-specific patch embeddings. We put forward the Transformer-based Knowledge Distillation (TransKD) framework which learns compact student transformers by distilling both feature maps and patch embeddings of large teacher transformers, bypassing the long pre-training process and reducing the FLOPs by >85.0%. Specifically, we propose two fundamental modules to realize feature map distillation and patch embedding distillation, respectively: 1) Cross Selective Fusion (CSF) enables knowledge transfer between cross-stage features via channel attention and feature map distillation within hierarchical transformers; 2) Patch Embedding Alignment (PEA) performs dimensional transformation within the patchifying process to facilitate the patch embedding distillation. Furthermore, we introduce two optimization modules to enhance the patch embedding distillation from different perspectives: 1) Global-Local Context Mixer (GL-Mixer) extracts both global and local information of a representative embedding; 2) Embedding Assistant (EA) acts as an embedding method to seamlessly bridge teacher and student models with the teacher’s number of channels. Experiments on Cityscapes, ACDC, NYUv2, and Pascal VOC2012 datasets show that TransKD outperforms state-of-the-art distillation frameworks and rivals the time-consuming pre-training method. The source code is publicly available athttps://github.com/RuipingL/TransKD.
Ruiping Liu 0001, Kailun Yang 0001, Alina Roitberg, Jiaming Zhang 0001, Kunyu Peng, Huayao Liu, Yaonan Wang 0001, Rainer Stiefelhagen
IEEE Trans. Intell. Transp. Syst.1
2023 Delivering Arbitrary-Modal Semantic Segmentation
abstract
Multimodal fusion can make semantic segmentation more robust. However, fusing an arbitrary number of modalities remains underexplored. To delve into this problem, we create the Deliver arbitrary-modal segmentation benchmark, covering Depth, LiDAR, multiple Views, Events, and RGB. Aside from this, we provide this dataset in four severe weather conditions as well as five sensor failure cases to exploit modal complementarity and resolve partial outages. To make this possible, we present the arbitrary cross-modal segmentation model CMNEXT. It encompasses a Self-Query Hub (SQ-Hub) designed to extract effective information from any modality for subsequent fusion with the RGB representation and adds only negligible amounts of parameters ~0.1M) per additional modality. On top, to efficiently and flexibly harvest discriminative cues from the auxiliary modalities, we introduce the simple Parallel Pooling Mixer (PPX). With extensive experiments on a total of six benchmarks, our CMNEXT achieves state-of-the-art performance on the Deliver, Kitti-360, MFNet, NYU Depth V2, UrbanLF, and MCubeS datasets, allowing to scale from 1 to 81 modalities. On the freshly collected Deliver, the quad-modal CMNEXT reaches up to 66.30% in mIoU with a +9.10% gain as compared to the mono-modal baseline.11The Deliver dataset and our code will be made publicly available at https://jamycheung.github.io/DELIVER.html.
Jiaming Zhang 0001, Ruiping Liu 0001, Hao Shi 0004, Kailun Yang 0001, Simon Reiß, Kunyu Peng, Haodong Fu, Kaiwei Wang, Rainer Stiefelhagen
CVPR2
2023 CMX: Cross-Modal Fusion for RGB-X Semantic Segmentation With Transformers
abstract
Scene understanding based on image segmentation is a crucial component of autonomous vehicles. Pixel-wise semantic segmentation of RGB images can be advanced by exploiting complementary features from the supplementary modality (${X}$-modality). However, covering a wide variety of sensors with a modality-agnostic model remains an unresolved problem due to variations in sensor characteristics among different modalities. Unlike previous modality-specific methods, in this work, we propose a unified fusion framework, CMX, for RGB-X semantic segmentation. To generalize well across different modalities, that often include supplements as well as uncertainties, a unified cross-modal interaction is crucial for modality fusion. Specifically, we design a Cross-Modal Feature Rectification Module (CM-FRM) to calibrate bi-modal features by leveraging the features from one modality to rectify the features of the other modality. With rectified feature pairs, we deploy a Feature Fusion Module (FFM) to perform sufficient exchange of long-range contexts before mixing. To verify CMX, for the first time, we unify five modalities complementary to RGB, i.e., depth, thermal, polarization, event, and LiDAR. Extensive experiments show that CMX generalizes well to diverse multi-modal fusion, achieving state-of-the-art performances on five RGB-Depth benchmarks, as well as RGB-Thermal, RGB-Polarization, and RGB-LiDAR datasets. Besides, to investigate the generalizability to dense-sparse data fusion, we establish an RGB-Event semantic segmentation benchmark based on the EventScape dataset, on which CMX sets the new state-of-the-art. The source code of CMX is publicly available athttps://github.com/huaaaliu/RGBX_Semantic_Segmentation.
Jiaming Zhang 0001, Huayao Liu, Kailun Yang 0001, Xinxin Hu, Ruiping Liu 0001, Rainer Stiefelhagen
IEEE Trans. Intell. Transp. Syst.5