California Partners for Advanced Transportation Technology

A new version of a field-deployable real-time laser-based detection system has been developed using new techniques of electronics and optics. The laser-based non-intrusive detection 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 speeds of both the front and rear of a vehicle are 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. A new version field prototype of a detection system for real-time measurement of delineations of moving vehicles for highway testing has been developed based on our previous research on the laboratory prototype of the system. The new version utilizes new techniques in electronics, optics and software. The testing results show that the new system can obtain the accuracy of measurement necessary to distinguish moving vehicles on the highway. It is an important step to approach the final goal of this project, described in the last report as developing a roadway detection system that can be used to gather reliable travel time data non-intrusively. The new system quantitatively proved that the principle of measurement is feasible, instead of qualitatively as did the last version system. Several tests have been done with the field prototype system on the highway. The software for real-time data acquisition, data processing and graphical user interface has been developed in the Windows NT system with RTX real-time extension. 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 new field prototype system. The measurement and calculation of laser power has been performed to ensure that the system is safe to expose to the public during field tests and future operation on the highway.