Sensing the Future of Traffic Detection-Part of the Series on ‘Lessons from the 2nd International Symposium in Freeway and Tollway Operations’ Conference in Hawaii

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The 2nd International symposium in Freeway and Tollway Operations was held in Honolulu, Hawaii from June 21-24, 2009. More than 200 experts specializing in freeway and tollway operations gathered from around the world to share their research knowledge and experiences. These series of articles summarize some of the major presentations with useful lessons for Hawaii. This is article 8 of 10.

Because of the continued increase in traffic demand and the costly construction of new transportation facilities, maximizing the efficiency of traffic management and capacity of traffic detection are becoming more and more vital. An alternative to expensive new highway construction is the implementation of Intelligent Transportation Systems (ITS) that combines real-time traffic information and communication technology with transportation infrastructure in an effort to relieve congestion, improve safety and to enhance the productivity and efficiency of urban transportation system.


Advanced traffic detection is one of the critical elements of ITS, which provides basic traffic information for developing strategies of traffic management and organization. The success of these strategies depends to a large extent on the proper deployment and maintenance of the traffic detector components of the overall transportation system.

A traffic detector is a traffic-actuated controller to register the presence, speed and classification of vehicles or pedestrians. The first traffic detector, which was installed in 1928 at a Baltimore intersection by a railway signal engineer, was activated by car horn. Modern traffic detectors include multiple sensing technologies, such as inductive-loop, magnetometers, video imaging and radar, laser, infrared ultrasonic and passive acoustic sensor.

Dr. Yinhai Wang from University of Washington, explained that traffic data are crucial for the success of ITS. Along with the development of sensing technology, traffic monitoring systems have advanced from point detection to range and segment detection.

Different types of traffic detectors are designed to provide traffic information concerning passage and presence of vehicles or pedestrians as well as other traffic flow parameters such as speed, occupancy, and classification. Road users value traffic information. There are wide applications of traffic information in traffic control and organization. For example, the traffic information about road conditions and route orientation from radio broadcasts, the internet and cell phones are extracted from the analysis of traffic data collected by traffic detectors.

Dr. Brian L. Smith at University of Virginia introduced an advanced High Occupancy Toll (HOT) lane management system, which consists of central traffic detectors and communication units to obtain and analyzes toll counts in order to estimate HOT lane vehicle density. Base on the HOT lane density, toll rates are re-evaluated every three minutes and rates are automatically adjusted within its preset ranges, between $0.25 and $8.00.

Millions of dollars have been spent on deployment of traffic detectors during the past 30 years in Hawaii. Nowadays, thousands of traffic sensors are deployed along the freeways, major arterials and intersections for traffic light signaling and collection of traffic information. Because of extensive deployment of traffic detectors, transportation managers and agencies benefit from improved ability to monitor, route and control vehicle flow and disseminate real-time information. However, these functions at operated at a very basic level in Hawaii.

An emerging potential technology to obtain reliable traffic data is from Bluetooth devices of cellular telephone. This detection technology provides an opportunity to collect high quality, high density travel times at a low cost. The Bluetooth detectors installed on the roadside receive Bluetooth signal from a vehicle containing a detectable Bluetooth device. The location of these vehicles can potentially be made available to traffic management agencies to anonymously track paths of vehicles. This information can be used in estimating congestion and travel time over wide areas. This technology has been tested on I-95 in Maryland and in Australia.

The more variable and unpredictable the traffic flow, the greater is the need for traffic detection. Inexpensive, automated traffic detection greatly increases the data availability for road users and road management.

‘Alyx (Xin) Yu is candidate for the Doctorate degree in Civil Engineering at the University of Hawaii at Manoa.’