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Detection Technology for IVHS

1. Scope of the Study

1.1 INTRODUCTION

Maximizing the efficiency and capacity of the existing ground transportation network is made necessary by the continued increase in traffic volume and the limited construction of new highway facilities in urban, intercity, and rural areas. Smart street systems that contain traffic monitoring detectors, real-time adaptive signal control systems, and motorist communications media are being combined with freeway and highway surveillance and control systems to create smart corridors that increase the effectiveness of the transportation network. The infrastructure improvements and new technologies are, in turn, being integrated with communications and displays in smart cars to form Intelligent Vehicle-Highway Systems (IVHS). Since the inception of this contract, Intelligent Transportation Systems (ITS) has replaced IVHS to represent the marriage of smart vehicles with smart infrastructure systems. As IVHS is included in the contract title, it is retained in this report.

Vehicle detectors are an integral part of nearly every modern traffic control system. Moreover, detectors and communications media will be major elements in future traffic monitoring systems. The types of traffic flow data, their reliability, consistency, accuracy, and precision and detector response time are some of the critical parameters to be evaluated when choosing a vehicle detector. These attributes become even more important as the number of detectors proliferate and the real-time control aspects of IVHS put a premium on both the quantity and quality of traffic flow data used in traffic surveillance and control algorithms.

Current vehicle detection is based predominantly on inductive loop detectors installed in the roadway subsurface. When properly installed and maintained, they can provide real-time data and a historical database against which to compare and evaluate more advanced detector systems. Alternative detector technologies being developed provide direct measurement of a wider variety of traffic parameters, such as density, travel time, and vehicle turning movement. These advanced detectors provide more accurate data; parameters that are not directly measured with previous instruments; inputs to area-wide surveillance and control of signalized intersections and freeways; and support of motorist information services. Furthermore, many of the advanced detector systems can be installed and maintained without disrupting traffic flow. The less obtrusive buried detectors will continue to find applications in the future, as for example, where aesthetic concerns are dominant or procedures are in place to monitor and repair malfunctioning units on a daily basis.

1.2 PROJECT OBJECTIVES

The objectives of the Federal Highway Administration (FHWA)-sponsored Detection Technology for IVHS project were to:

• Determine the traffic parameters and their corresponding accuracy specifi-cations needed for future IVHS applications;
• Perform laboratory and field tests with detectors that apply technologies compatible with above-the-road, surface, and subsurface mounting to determine the ability of state-of-the-art detectors to measure traffic parameters with acceptable accuracy, precision, and repeatability;
• Determine the need and feasibility of establishing permanent vehicle detector test facilities.

In performing the technology evaluations and in analyzing the data, focus was placed on the underlying technology upon which the detectors were based. It was not the purpose of the program to determine which specific detectors met a set of requirements, but rather whether the sensing technology they used had merit in measuring and reporting traffic data to the accuracy needed for present and future applications. Obviously, there can be many implementations of a technology, some of which may be better exploited than others at any time. Thus, a technology may show promise for future applications, but the state-of-the-art of current hardware or software may be hampering its present deployment.

The project consisted of 12 major tasks:

Task A. Develop a working paper that defines IVHS traffic parameter specifications for the following application areas:

• Interconnected Intersection Control,
• Isolated Intersection Control,
• Freeway Incident Detection,
• Traffic Data Collection,
• Real-Time Traffic Adaptive Control,
• Vehicle-Roadway Communications.

Task B. Select sites for detector field tests. Test sites in three different regions of the country will be selected to provide a range of environmental and traffic conditions broad enough to ensure the utility of the test results on a nationwide basis.

Task C. Develop vehicle detector laboratory test specifications and a laboratory test plan.

Task D. Select and obtain vehicle detectors for testing.

Task E. Conduct laboratory detector tests and generate a report describing the results.

Task F. Develop vehicle detector field test specifications and field test plan.

Task G. Install vehicle detectors at field test sites and collect detection technology evaluation data.

Task H. Generate detection technology field test results.

Task I. Determine which of the currently available vehicle detectors meet the IVHS criteria of Task A.

Task J. Determine the need and feasibility of establishing permanent vehicle detector test facilities.

Task K. Prepare a draft final report.

Task L. Prepare the final report that incorporates comments received from FHWA and others.

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