Vehicular networking has significant potential to enable diverse applications associated with traffic safety, traffic efficiency and infotainment. In this survey and tutorial paper we introduce the basic characteristics of vehicular networks, provide an overview of applications and associated requirements, along with challenges and their proposed solutions. In addition, we provide an overview of the current and past major ITS programs and projects in the USA, Japan and Europe. Moreover, vehicular networking architectures and protocol suites employed in such programs and projects in USA, Japan and Europe are discussed.

Vehicular Networking: A Survey and Tutorial on Requirements, Architectures, Challenges, Standards and Solutions

Recent advances in hardware, software, and communication technologies are enabling the design and implementation of a whole range of different types of networks that are being deployed in various environments. One such network that has received a lot of interest in the last couple of years is the Vehicular Ad-Hoc Network (VANET). VANET has become an active area of research, standardization, and development because it has tremendous potential to improve vehicle and road safety, traffic efficiency, and convenience as well as comfort to both drivers and passengers. Recent research efforts have placed a strong emphasis on novel VANET design architectures and implementations. A lot of VANET research work have focused on specific areas including routing, broadcasting, Quality of Service (QoS), and security. We survey some of the recent research results in these areas. We present a review of wireless access standards for VANETs, and describe some of the recent VANET trials and deployments in the US, Japan, and the European Union. In addition, we also briefly present some of the simulators currently available to VANET researchers for VANET simulations and we assess their benefits and limitations. Finally, we outline some of the VANET research challenges that still need to be addressed to enable the ubiquitous deployment and widespead adoption of scalable, reliable, robust, and secure VANET architectures, protocols, technologies, and services.

Vehicular ad hoc networks (VANETS): status, results, and challenges

Since the early 1980s, short-term traffic forecasting has been an integral part of most Intelligent Transportation Systems (ITS) research and applications; most effort has gone into developing methodologies that can be used to model traffic characteristics and produce anticipated traffic conditions. Existing literature is voluminous, and has largely used single point data from motorways and has employed univariate mathematical models to predict traffic volumes or travel times. Recent developments in technology and the widespread use of powerful computers and mathematical models allow researchers an unprecedented opportunity to expand horizons and direct work in 10 challenging, yet relatively under researched, directions. It is these existing challenges that we review in this paper and offer suggestions for future work.

Short-term traffic forecasting: Where we are and where we’re going

This article presents a comprehensive survey of the state-of-the-art for vehicle ad hoc networks. We start by reviewing the possible applications that can be used in VANETs, namely, safety and user applications, and by identifying their requirements. Then, we classify the solutions proposed in the literature according to their location in the open system interconnection reference model and their relationship to safety or user applications. We analyze their advantages and shortcomings and provide our suggestions for a better approach. We also describe the different methods used to simulate and evaluate the proposed solutions. Finally, we conclude with suggestions for a general architecture that can form the basis for a practical VANET.

Vehicle Ad Hoc networks: applications and related technical issues

Vehicular Ad Hoc Networks: A New Challenge for Localization-Based Systems

This article presents an overview of highway cooperative collision avoidance (CCA), which is an emerging vehicular safety application using the IEEE- and ASTM-adopted Dedicated Short Range Communication (DSRC) standard. Along with a description of the DSRC architecture, we introduce the concept of CCA and its implementation requirements in the context of a vehicle-to-vehicle wireless network, primarily at the Medium Access Control (MAC) and the routing layer. An overview is then provided to establish that the MAC and routing protocols from traditional Mobile Ad Hoc networks arc not directly applicable for CCA and similar safety-critical applications. Specific constraints and future research directions are then identified for packet routing protocols used to support such applications in the DSRC environment. In order to further explain the interactions between CCA and its underlying networking protocols, we present an example of the safety performance of CCA using simulated vehicle crash experiments. The results from these experiments arc also used to demonstrate the need for network data prioritization for safety-critical applications such as CCA. Finally, the performance sensitivity of CCA to unreliable wireless channels is discussed based on the experimental results.

Vehicle-to-vehicle wireless communication protocols for enhancing highway traffic safety

Vehicle emissions in congestion: Comparison of work zone, rush hour and free-flow conditions

The paper describes a low-pass adaptive filtering algorithm for predicting average roadway travel times using automatic vehicle identification (AVI) data. The algorithm is unique in three aspects. First, it is designed to handle both stable (constant mean) and unstable (varying mean) traffic conditions. Second, the algorithm can be successfully applied for low levels of market penetration (less than 1%). Third, the algorithm works for both freeway and signalized arterial roadways. The proposed algorithm utilizes a robust data-filtering procedure that identifies valid data within a dynamically varying validity window. The size of the validity window varies as a function of the number of observations within the current sampling interval, the number of observations in the previous intervals, and the number of consecutive observations outside the validity window. Applications of the algorithm to two AVI datasets from San Antonio, one from a freeway link and the other from an arterial link, demonstrate the ability of the proposed algorithm to efficiently track typical variations in average link travel times while suppressing high frequency noise signals.

http://m.cotrip.org/AVI_Filter_Paper_v5_TR.pdf

Estimating dynamic roadway travel times using automatic vehicle identification data for low sampling rates

This paper proposes a broadcast based packet forwarding mechanism for intra-platoon cooperative collision avoidance (CCA) using dedicated short range communication (DSRC) links. The paper first motivates the needs for broadcast forwarding as opposed to unicast routing for transporting inter-vehicle data for safety-critical applications. Then it introduces an implicit acknowledgement mechanism for reducing the amount of broadcast traffic for enhanced packet delivery rate. We have developed a discrete event hybrid simulator InventSim, which is capable of jointly simulating DSRC based vehicular wireless networks, highway vehicle traffic with car following logic and various drivers' reaction models, and ITS application interface to the wireless network. Performance of the proposed broadcast forwarding for a CCA system has been characterized using InventSim. Reported results demonstrate that with inter-vehicle spacing of nearly one second, the proposed mechanism is capable of saving up to 90% of vehicles in a platoon from chain crashes following emergency events at the front of the platoon. The system has been also evaluated for a wide range of parameters including vehicle spacing, drivers' reaction time, and the amount of background non-CCA traffic

Cooperative vehicle collision avoidance using inter-vehicle packet forwarding

This paper presents an effort to develop a virtual testbed for assessing probe vehicle data generation by IntelliDrive vehicles within a microscopic traffic-simulation environment. Simulation capabilities are implemented through the development of a portable plug-in module using the application programming interface of the Paramics microscopic traffic simulation. This module simulates the generation of snapshots by individual vehicles, the uploading of these snapshots to roadside units, and some probe vehicle data postprocessing. While some temporary simplifying assumptions are made, the simulation generally follows operational concepts described in the Society of Automotive Engineers (SAE) J2735 Surface Vehicle Standard. Application of the model is demonstrated by simulating IntelliDrive probe data collection over the U.S. Department of Transportation (USDOT)'s Michigan Proof-of-Concept testbed. Simulation results show the sensitivity of probe data collection to communication range, market penetration, number of active roadside communication units (RSEs), interval between snapshots, and snapshot buffer size. Impacts on link travel time estimates are also presented. These results clearly demonstrate the utility of the simulator in conducting evaluations and sensitivity analyses for scenarios that would be difficult to execute in existing testbeds.

Francois Dion

Papers

Vehicle-to-vehicle wireless communication protocols for enhancing highway traffic safety

Vehicle emissions in congestion: Comparison of work zone, rush hour and free-flow conditions

Estimating dynamic roadway travel times using automatic vehicle identification data for low sampling rates

Cooperative vehicle collision avoidance using inter-vehicle packet forwarding

Virtual Testbed for Assessing Probe Vehicle Data in IntelliDrive Systems