Traffic Flow Estimation Based on Three-layer Stacking Model

Traffic sensing systems rely more and more on user generated (insecure) data, which can pose a security risk whenever the data is used for traffic flow control. In this article, we propose a new formulation for detecting malicious data injection in traffic flow monitoring systems by using the underlying traffic flow model. The state of traffic is modeled by the Lighthill-Whitham- Richards traffic flow model, which is a first order scalar conservation law with concave flux function. Given a set of traffic flow data, we show that the constraints resulting from this partial differential equation are mixed integer linear inequalities for some decision variable. We use this fact to pose the problem of detecting spoofing cyber-attacks in probe-based traffic flow information systems as mixed integer linear feasibility problem. The resulting framework can be used to detect spoofing attacks in real time, or to evaluate the worst-case effects of an attack offline. A numerical implementation is performed on a cyber-attack scenario involving experimental data from the Mobile Century experiment and the Mobile Millennium system currently operational in Northern California. © 2013 IEEE.

Vision‐based traffic surveillance plays an important role in traffic management. However, outdoor illuminations, the cast shadows and vehicle variations often create problems for video analysis and processing. Thus, the authors propose a real‐time cost‐effective traffic monitoring system that can reliably perform traffic flow estimation and vehicle classification at the same time. First, the foreground is extracted using a pixel‐wise weighting list that models the dynamic background. Shadows are discriminated utilising colour and edge invariants. Second, the foreground on a specified check‐line is then collected over time to form a spatial–temporal profile image. Third, the traffic flow is estimated by counting the number of connected components in the profile image. Finally, the vehicle type is classified according to the size of the foreground mask region. In addition, several traffic measures, including traffic velocity, flow, occupancy and density, are estimated based on the analysis of the segmentation. The availability and reliability of these traffic measures provides critical information for public transportation monitoring and intelligent traffic control. Since the proposed method only process a small area close to the check‐line to collect the spatial–temporal profile for analysis, the complete system is much more efficient than existing visual traffic flow estimation methods.

Predicting urban traffic flow is of big significant to traffic management and public security. However, with the continuous expansion of urban areas and the development of data acquisition technology, new types of traffic data are characterized by wide spatial distribution, high timeliness and large data volume. Traffic flow forecasting requires high cost and related domain knowledge. Therefore, it has become an urgent research topic to properly use a small amount of traffic data to efficiently construct a traffic prediction model. In this paper, we propose a generative adversarial network-based traffic flow prediction method called RT-GAN which is the real-time prediction of traffic flows in the surroundings area according to the traffic information in the central area. The combination of gated convolution and dilated convolution can capture the traffic information in the near and far regions and perform feature fusion to achieve real-time prediction. Experiments on the Beijing and New York traffic flow data sets show that our method outperforms others, providing a potential solution to practical applications.

Real-time citywide reconstruction of traffic flow from moving cameras on lightweight edge devices

Traffic incidents continue to cause a significant loss in deaths, injuries, and property damages. Reported traffic accident data contains a considerable amount of human errors, hindering the studies on traffic accidents. Several approaches have been developed to detect accidents using traffic data in real time. However, those approaches do not consider the spatiotemporal patterns inherent in traffic data, resulting in high false alarm rates. In this paper, we study the problem of traffic accident detection by considering multiple traffic speed time series collected from road network sensors. To capture the spatiotemporal impact of traffic accidents to upstream locations, we adopt Impact Interval Grouping (IIG), which compares real-time traffic speed with historical data, and generates impact intervals to determine the presence of accidents. Furthermore, we take a multivariate time series classification approach and extract three novel features to measure the severity of traffic accidents. We use real-world traffic speed and accident datasets in our empirical evaluation, and our solutions outperform state-of-the-art approaches in multivariate time series classification.

Traffic data are the fundamental inputs to traffic flow analysis and simulation studies, which facilitate decision making in the fi eld of traffic engineering. Hence, the accuracy of traffic data is of paramount importance. This study compares new technologies available for traffic data collection considering their accuracy and applicability in the Sri Lankan context. Traffic in Sri Lanka is of heterogeneous nature, as opposed to the homogeneous nature observed in most developed countries. Hence, collection of traffic data poses several challenges that affects its accuracy. Three techniques, the infrared driven TIRTL instrument, the video image processing-based TRAZER application and the traffic data collection method using the Google distance matrix application programming interface (API), with respect to their data collection accuracy are reviewed in this study. The fundamental macroscopic traffic data variables (fl ow and speed) were evaluated against control surveys. It was found that each technology has its strengths and weaknesses and needs to be used appropriately. The TIRTL instrument fared better on road sections on level terrain when the crossfall did not obstruct the infrared beams. Such occasions provided a rich set of microscopic traffic data. The TRAZER software delivered data up to a 100 % accuracy. However, this required the user to go through a lengthy postprocessing routine to extract the final set of traffic data. Google traffic data collection provides highly accurate results when estimating link speeds. This method is ideal for collection of bulk data with spatio-temporal variations and the process can be fully automated to reduce the human resource requirement.

Traffic estimation and traffic simulation are essential parts of the intelligent transportation system. In recent years, massive traffic data has brought many data-based traffic estimation methods, but few are utilized in traffic simulation. The cause is that the data-based traffic simulation has high requirements for data quality, needing the trip information of all vehicles, not met by common traffic data. Fortunately, the electronic registration identification (ERI) data of the vehicle can satisfy. Therefore, we utilize ERI data to study the traffic estimation and simulation for the road network. The core of this research is the travel time estimation model, which is constructed by combining traffic theory models and the deep neural network. The traffic theory models are a group of linear models, which represent the relationship between traffic flow or traffic density and travel time. The deep neural network can extract the temporal and spatial characteristics of the road network traffic by Moving Average Convergence-Divergence (MACD) and Graph Convolutional Network (GCN), respectively. We named the travel time estimation model MGCN. Then, we employed MGCN for traffic simulation. In the experiment section, we employed Chongqing ERI data to verify the research content. Compared with some baseline methods, our method is superior in travel time estimation and traffic simulation.

This paper provides a review of a 3-year research program on the feasibility of using airborne LiDAR (Light Detection and Ranging) and imagery collected simultaneously over transportation corridors for estimation of traffic flow parameters such as: (1) vehicle counts, (2) vehicle classification, (3) velocity per vehicle category, and (4) intersection movement patterns. This work is conducted by The National Consortium for Remote Sensing in Transportation-Flows (NCRST-F), led by The Ohio State University, supported by the U.S. Department of Transportation and the National Aeronautics and Space Administration (NASA). The major focus is on improving the efficiency of transportation systems by integration of remotely sensed data with traditional ground data to monitor and manage traffic flows.

Estimating traffic flow condition is a tough but beneficial task. In Intelligent Transportation System (ITS), many applications have been done to collect and analyze traffic data. However, the surveillance video data are still only used for engineer's manual check. To better utilize this data source, traffic flow estimation from surveillance camera should be explored. This study uses Faster Regional Convolutional Neural Network (Faster R-CNN) with ResNet 101 as the backbone to achieve multi-object detection. Then a tracking algorithm based on histogram comparison is applied to link objects across frames. Finally, this study uses warping method to convert vehicle speeds from the pixel domain to the real world. The results show that estimating vehicle speed at intersection is more challenging than in uninterrupted flow.

Dynamic multi-scale spatial-temporal graph convolutional network for traffic flow prediction

Data missing remains a difficult and important problem in the transportation information system, which seriously restricts the application of the intelligent transportation system (ITS), dominatingly on traffic monitoring, e.g., traffic data collection, traffic state estimation, and traffic control. Numerous traffic data imputation methods had been proposed in the last decade. However, lacking of sufficient temporal variation characteristic analysis as well as spatial correlation measurements leads to limited completion precision, and poses a major challenge for an ITS. Leveraging the low-rank nature and the spatial-temporal correlation of traffic network data, this paper proposes a novel approach to reconstruct the missing traffic data based on low-rank matrix factorization, which elaborates the potential implications of the traffic matrix by decomposed factor matrices. To further exploit the temporal evolvement characteristics and the spatial similarity of road links, we design a time-series constraint and an adaptive Laplacian regularization spatial constraint to explore the local relationship with road links. The experimental results on six real-world traffic data sets show that our approach outperforms the other methods and can successfully reconstruct the road traffic data precisely for various structural loss modes.

Accurate predictive modeling of traffic flow is critically important as it allows transportation users to make wise decisions to circumvent traffic congestion regions. The advanced development of sensing technology makes big data more affordable and accessible, meaning that data-driven methods have been increasingly adopted for traffic flow prediction. Although numerous data-driven methods have been introduced for traffic flow predictions, existing data-driven methods cannot consider the correlation of the extracted high-dimensional features and cannot use the most relevant part of the traffic flow data to make predictions. To address these issues, this work proposes a decoder convolutional LSTM network, where the convolutional operation is used to consider the correlation of the high-dimensional features, and the LSTM network is used to consider the temporal correlation of traffic flow data. Moreover, the multi-head attention mechanism is introduced to use the most relevant portion of the traffic data to make predictions so that the prediction performance can be improved. A traffic flow dataset collected from the Caltrans Performance Measurement System (PeMS) database is used to demonstrate the effectiveness of the proposed method.

Nowadays, traffic flow estimation is the one of the most important topics in intelligent transportation systems (ITS). Accordingly, the authors of this article propose a traffic flow estimation method using time-series analysis and geometric correlation. Firstly, they define a 3D heat-map to present the traffic state and spatial and temporal adjacent traffic condition. Thereafter, they model the dependency heat-map using spatiotemporal Markov Random Field and estimate the probability using logistic regression. To evaluate the performance of the proposed method, it was tested using data collected from expressway traffic that were provided by the Korean Expressway Corporation, and its performance was compared with those of other existing approaches. The results showed that the proposed method has a superior accuracy to others method, which has the accuracy of 85%.

During the last decades, "Transport Demand" and "Mobility" has been a continuously developing branch in the transport literature.This is reflected in the great amount of research papers published in scientific magazines dealing with trip matrix estimation (see (Doblas & Benítez, 2005)) and traffic assignment problems (see (Praskher & Bekhor, 2004)).Current traffic models reproduce the mobility using several data inputs, in particular prior trip matrix, link counts, etc. (see (Yang & Zhou, 1998)) which are data only from a subset of the problem variables, and its size will depend on the available budget for the study being carried on.Among the problems faced for solving these models we can emphasize the high number of possible solutions which is usually solved by choosing the solution where the model results best fits real data.Nevertheless a model does not have to reproduce only the real data, but also must reproduce accurately all the variables.To this end, the aim of this paper consists of presenting two Bayesian network models for traffic estimation, trying to bring a new tool to the transportation field.The first one deals with the problem of link flows, trip matrix estimation and traffic counting location and in the second one we propose a Bayesian network for route flow estimation (and hence link flows and OD flows) using data from plate scanning technique together with a model for optimal plate scanning device location.Since a Gaussian Bayesian network is used, these models allow us to update the predictions from a small subset of real data and probability intervals or regions are obtained to get an idea of the associated uncertainties.In addition dealing with data from the plate scanning approach we improve the under-specification level of the traffic flow estimation problem. Some background on Bayesian network modelsA Bayesian network (see, (Castillo et al., 1999)) is a pair (G, P ), where G is a directed acyclic graph (DAG) defined on a set of nodes X (the random variables), and P = {p(x 1 |π 1 ), . . ., p(x n |π n )} is a set of n conditional probability densities (CPD), one for each variable, and Π i is the set of parents of node X i in G.The set P defines the associated joint 19 www.intechopen.comBayesian Network 318 probability density of all nodes as p(1)The graph G contains all the qualitative information about the relationships among the variables, no matter which probability values are assigned to them 1 .Complementary, the probabilities in P contain the quantitative information, i.e., they complement the qualitative properties revealed by the graphical structure.

Accurate on-road vehicle speed prediction is important for many intelligent vehicular and transportation applications. It is also challenging because the individual vehicle speed is affected by many factors, e.g., traffic speed, vehicle type, and driver's behavior, in either deterministic or stochastic ways. This paper proposes a novel vehicle speed prediction method in the context of vehicular networks, where the real-time traffic information is accessible. Traffic speeds of following road segments are first predicted by Neural Networks (NNs) based on historical traffic data. Hidden Markov models (HMMs) are trained by the Baum-Welch algorithm with historical traffic and vehicle data to present the statistical relationship between vehicle speed and traffic speed. The forward-backward algorithm is applied on HMMs to extract vehicle's speed on each road segment along the driving route. Simulation is set up on the SUMO microscopic traffic simulator with the application of a real Luxembourg highway network and traffic count data. The vehicle speed prediction result shows that our proposed method outperforms other ones in terms of prediction accuracy.