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Open Access Publications from the University of California

Development and Testing of Field-Deployable Real-Time Laser-Based Non-Intrusive Detection System for Measurement of True Travel Time on the Highway

  • Author(s): Cheng, Harry H.
  • Shaw, Ben
  • Palen, Joe
  • Hu, Xudong
  • Lin, Bin
  • Larson, Jonathan E.
  • Van Katwyk, Kirk
  • et al.

We have developed a field prototype of a laser-based non-intrusive detection system for real-time measurement of delineations of moving vehicles for highway testing, based on our previous research on the laboratory prototype of the system. The primary goal of this project is to develop a roadway detection system that can be used to gather reliable travel time data non-intrusively. The system uses a laser line that is projected onto the ground as a probe. The reflected light is collected and focused into a photodiode array by an optical system. Vehicle presence is detected based on the absence of reflected laser light. By placing two identical laser/sensor pairs at a known distance apart, the speed of both the front and rear of a vehicle is measured based on the times when each sensor is triggered. The length of each vehicle is determined by using these speed measurements and the residence time of the vehicle under each sensor. We have built a field prototype detection system which is used not only to proof the concept and algorithm of the detection system, but also to test the system in the real traffic environment. Several tests have been done with the field prototype system on the highway, and the test results further verified that the principle of our detection system is technically sound and indicated that the algorithm implemented in the software works in most cases. The software for the real-time data acquisition, data processing and graphic user interface has been developed in a real-time operating system. In the software, the speed, acceleration, and length of a detected vehicle can be calculated and displayed simultaneously. This document describes the design and implementation of each functional component and software of the field prototype system. The measurement and calculation of laser power has been performed to ensure that the system is safe to expose to public during the field tests and future operation on the highway.

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