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South Dakota Department of Transportation
Project Synopsis

Title: Verification of Radar Vehicle Detection Equipment
Project Researcher: Nathan Weber, SDDOT
Project Manager: Dan Strand
Research Period: 5/1/1998 - 4/30/1999
Cost: $10,000.00

Problem Statement: The Office of Data Inventory is responsible for monitoring traffic throughout the state. Permanent equipment has been installed at 52 sites on various highways to count and report the volume of traffic flow. This permanent equipment is in the form of inductive loops which are embedded in the roadway. As these sites deteriorate, and when the need for new sites arise, new equipment must be installed into the pavement. This requires closing lanes of traffic and sawing cuts into the pavement to install the equipment. Currently, there is equipment available that does not damage the pavement, would not cause driver delays from lane closures, and does not risk the safety of staff by exposing them to traffic during in-pavement installations. This new, non-intrusive equipment can be collectively referred to as radar vehicle detection equipment. The specific system which is being studied is a Microwave Doppler sensor.

In order to properly compare the two traffic counting systems, both the radar vehicle detection equipment and the inductive loops should be evaluated for their reliability and cost effectiveness.

Findings: Currently, inductive loops are used to count traffic at the 52 permanent sites located in South Dakota. Because they are located within the pavement, the loops are susceptible to being destroyed during maintenance projects. When they are destroyed, it is necessary to close traffic in that lane, cut a loop into the pavement, and fill the void left in the concrete. This study explored the potential implementation of a non-intrusive sensor, the RTMS. The RTMS is installed adjacent to the roadway so it is not at risk of being destroyed when maintenance is performed. In this study, the RTMS was evaluated for both its cost effectiveness and reliability. From manual counts, it was found that the RTMS tended to count 3 percent low. It was more accurate than road tubes, which were also used to compare to the manual counts. According to the Office of Data Inventory, the accuracy of the inductive loops is dependent on the counters that they are run through. The initial cost of the RTMS tends to be higher than that of inductive loops. But, if the pavement is in poor condition, it is probable that the loops will be in need of replacement before the end of their expected lifetime. This will cause the lifetime cost of the inductive loops to be more than that of the RTMS. In the case of speed surveys, the inductive loops are far less expensive to implement than the RTMS. Due to its reliability, it was determined that the RTMS should be implemented if it is cost effective. In other words, if the lifetime cost of implementing the RTMS is less than or comparable to that of the inductive loops, it should be implemented. Otherwise, the inductive loops should be reinstalled at that location. Other potential implementations of the RTMS, such as a mobile counting station, were explored as well. Due to problems the Minnesota DOT found with the predecessor to the RTMS used in this study, it is recommended that further testing be done on the RTMS to verify that it counts traffic accurately during snow, rain, and freezing rain.

Research Objectives:
1  To compare the traffic counts found by a Microwave Doppler sensor over seven distinctive lanes of traffic to those counts produced by inductive loops and manual counting.
2  To determine the cost effectiveness of the Microwave Doppler sensor compared to that of the inductive loops for both rural and urban situations.

Research Tasks:
1  Meet with the project’s technical panel to review the project scope and work plan.
2  Conduct a literature search to obtain knowledge about the installation, ability, and use of Microwave Doppler systems.
3  Participate in manufacturer’s training on use and installation of non-intrusive sensor.
4  Get recommendations for installation of Microwave Doppler systems from EIS representative.
5  Determine the exact height and distance from the road where the sensor will be placed.
6  Install the non-intrusive sensor.
7  Perform manual traffic counts and compare the data to that of inductive loops and Microwave Doppler sensors.
8  Determine the cost of installing inductive loops, and compare it to the cost of the non-intrusive system.
9  Review data and prepare recommendations for future implementation.
10  Prepare a final report and executive summary of the literature review, research methodology, findings, conclusions, and recommendations.
11  Make an executive presentation to the SDDOT Research Review Board at conclusion of the project.

Documents Available:

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