Vision-based traffic surveys in urban environments

This paper presents a state-of-the-art, vision-based vehicle detection and type classification to perform traffic surveys from a roadside closed-circuit television camera. Vehicles are detected using background subtraction based on a Gaussian mixture model that can cope with vehicles that become stationary over a significant period of time. Vehicle silhouettes are described using a combination of shape and appearance features using an intensity-based pyramid histogram of orientation gradients (HOG). Classification is performed using a support vector machine, which is trained on a small set of hand-labeled silhouette exemplars. These exemplars are identified using a model-based preclassifier that utilizes calibrated images mapped by Google Earth to provide accurately surveyed scene geometry matched to visible image landmarks. Kalman filters track the vehicles to enable classification by majority voting over several consecutive frames. The system counts vehicles and separates them into four categories: car, van, bus, and motorcycle (including bicycles). Experiments with real-world data have been undertaken to evaluate system performance and vehicle detection rates of 96.45% and classification accuracy of 95.70% have been achieved on this data.The authors gratefully acknowledge the Royal Borough of Kingston for providing the video data. S.A. Velastin is grateful to funding received from the Universidad Carlos III de Madrid, the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement nº 600371, el Ministerio de Economía y Competitividad (COFUND2013-51509) and Banco Santander

Performance Measure That Indicates Geometry Sufficiency of State Highways: Volume II—Clear Zones and Cross-Section Information Extraction

Evaluation method employed for the proposed corridor projects by Indiana Department of Transportation (INDOT) consider road geometry improvements by a generalized categorization. A new method which considers the change in geometry improvements requires additional information regarding cross section elements. Part of this information is readily available but some information like the embankment slopes and obstructions near traveled way needs to be acquired. This study investigates available data sources and methods to obtain cross-section and clear zone information in a feasible way for this purpose. We have employed color infrared (CIR) orthophotos, LiDAR point clouds, digital elevation and surface models for the extraction of the paved surface, average grade, embankment slopes, and obstructions near the traveled way like trees and man-made structures. We propose a framework which first performs a support vector machine (SVM) classification of the paved surface, then determines the medial axis and reconstructs the paved surface. Once the paved surface is obtained, the clear zones are defined and the features within the clear zones are extracted by the classification of LiDAR point clouds. SVM classification of the paved surface from CIR orthophotos in the study area results with a classification accuracy over 90% which suggests the suitability of high resolution CIR images for the classification of paved surface via SVM. A total of 21.3 miles of relevant road network has been extracted. This corresponds to approximately 90% of the actual road network due to missing parts in the paved surface classification results and parts which were removed during cleaning, simplification and generalization process. Branches due to connecting driveways, adjacent parking lots, etc. were also extracted together with the main road alignment as by-product. This information may also be utilized if found necessary with further effort to filter out irrelevant pieces that do not correspond to any actual branches. Based on the extracted centerline and classification results, we have estimated the paved surface as observed on the orthophotos. Based on the estimated paved surface centerline and width, we have generated cross section lines and calculated the side slopes. We have extracted the buildings and trees within the clear-zones that are also defined based on the reconstruction of the paved surface. Among 86 objects detected as buildings, 14% were false positives due to confusion with bridges or trees which present planar structure

Advances and Applications of Computer Vision Techniques in Vehicle Trajectory Generation and Surrogate Traffic Safety Indicators

The application of Computer Vision (CV) techniques massively stimulates microscopic traffic safety analysis from the perspective of traffic conflicts and near misses, which is usually measured using Surrogate Safety Measures (SSM). However, as video processing and traffic safety modeling are two separate research domains and few research have focused on systematically bridging the gap between them, it is necessary to provide transportation researchers and practitioners with corresponding guidance. With this aim in mind, this paper focuses on reviewing the applications of CV techniques in traffic safety modeling using SSM and suggesting the best way forward. The CV algorithm that are used for vehicle detection and tracking from early approaches to the state-of-the-art models are summarized at a high level. Then, the video pre-processing and post-processing techniques for vehicle trajectory extraction are introduced. A detailed review of SSMs for vehicle trajectory data along with their application on traffic safety analysis is presented. Finally, practical issues in traffic video processing and SSM-based safety analysis are discussed, and the available or potential solutions are provided. This review is expected to assist transportation researchers and engineers with the selection of suitable CV techniques for video processing, and the usage of SSMs for various traffic safety research objectives

Non-parametric spatially constrained local prior for scene parsing on real-world data

Scene parsing aims to recognize the object category of every pixel in scene images, and it plays a central role in image content understanding and computer vision applications. However, accurate scene parsing from unconstrained real-world data is still a challenging task. In this paper, we present the non-parametric Spatially Constrained Local Prior (SCLP) for scene parsing on realistic data. For a given query image, the non-parametric SCLP is learnt by first retrieving a subset of most similar training images to the query image and then collecting prior information about object co-occurrence statistics between spatial image blocks and between adjacent superpixels from the retrieved subset. The SCLP is powerful in capturing both long- and short-range context about inter-object correlations in the query image and can be effectively integrated with traditional visual features to refine the classification results. Our experiments on the SIFT Flow and PASCAL-Context benchmark datasets show that the non-parametric SCLP used in conjunction with superpixel-level visual features achieves one of the top performance compared with state-of-the-art approaches.Comment: 10 pages, journa