Joe Palen

A real-time laser-based detection system for measurement of delineations of moving vehicles

In current practice, quantitative traffic data are most commonly acquired from inductive loops. In addition, video-image processing or time-of-flight laser systems can be used. These methods all have problems associated with them. We have developed a nonintrusive laser-based detection system for measurement of vehicle travel time. The basic detector unit consists of a fan angle laser and a photodetector array positioned above the plane of detection. This detection system is able to determine the length and width of moving objects in real time with high resolution, with the highest resolution measurements being associated with object lengths. This information is used to differentiate similar objects and can be used later for re-identification of individual objects or object groups, providing a real measure of travel time between detection sites.

Development and field test of a laser-based nonintrusive detection system for identification of vehicles on the highway

A real-time laser-based nonintrusive detection system has been developed for the measurement of true travel time of vehicles on the highway. The 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. Using real-time software, the speed, acceleration, and length of a detected vehicle can be calculated and displayed simultaneously. A new prototype system has been tested on the highway with different types of vehicles and scenarios, and the results are presented here. The tests have also been carried out for different weather conditions and road materials. The results indicate that the laser system operates well under real highway conditions.

Optical and electronic design for a field prototype of a laser-based vehicle delineation detection system

A field prototype of a laser-based non-intrusive vehicle detection system has been developed for the measurement of delineations of moving vehicles on the highway. This prototype is based on our previous research on the principle of the measurement. The detection system uses two laser lines that are projected onto the ground as probes. The reflected light is collected and focused onto 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 can be calculated based on the times when each sensor is triggered. The detector data are acquired and processed by a real-time system to obtain speed, acceleration, and length of a detected vehicle. The travel time of a vehicle can be acquired by detecting a vehicle at the beginning of a link and re-identifying the same vehicle at the end of the link. Several tests have been done with the field prototype system on the highway. The testing results show that the system can obtain the accuracy of measurement necessary to distinguish between moving vehicles on the highway. This article describes the design and implementation of each functional component of an advanced version of the field prototype system.

Performance Analysis for Design of a High-Precision Electronic Opto-Mechanical System for Vehicle Delineation Detection on Highway

We have developed a laser photodiode array based detection system that can non-intrusively detect delineations of vehicles on the highway. The U.S. Patent Office has recently approved a patent for this detection system. The system is built with low-cost off-the-shelf opto-mechanical components. The error sources from a system design point of view will be analyzed in this paper. Our study indicates that the frequency of pulsed laser diodes, computer-sampling rates, deviations in the angle of laser light and imperfectly matched detection points for sensor pairs are the main sources of error in the detection system.

Estimating Traffic Speed with Single Inductive Loop Event Data

The estimation of traffic speed based on loop detector occupancy is a long-standing problem that is critical to traffic management and control. Single-loop detector stations are still popular in highway traffic systems in practice. Although dual loop stations could generate more accurate speed estimation with event data, updating single loops to dual loops is costly. Most previous work, such as the g-factor method on speed estimation with a single-loop system, used aggregated data and assumed a known effective vehicle length. However, those methods did not always produce good results, particularly in traffic transition phases. This paper proposes a new approach using event data and mode occupancy within a moving window of variable length to estimate the effective vehicle length, or g-factor. Berkeley Highway Laboratory dual loop data with a 1-Hz update rate and 60-Hz information were used for algorithm validation and reliability tests. The speed estimated from the corrected dual loop data was used as the ground truth for comparison. Root mean square error was used to quantify the discrepancy. Results showed that the proposed approach generates very satisfactory speed estimations compared with estimations from dual loop stations. This algorithm can be run at the control-cabinet level, in which event data of an individual loop from a 170 or 2070 controller are available without the need of any hardware modification. These controllers have the processor capabilities to handle data in real time.

Agent-Based Real-Time Computing and Its Applications in Traffic Detection and Management Systems

This paper studies the generic architecture and coordination mechanism of an FIPA (Foundation for Intelligent Physical Agents) compliant heterogeneous multi-agent system (MAS) in a distributed control scenario. Proposed generic MAS framework has been applied to a real-time traffic detection and management system. The agent-based real-time traffic detection and management system (ABRTTDMS) is designed for the information fusion of different traffic detection systems on highways to optimize real-time traffic detection and management. ABRTTDMS is a multi-level agent system. The lowest level agents are responsible for processing the real-time traffic data and monitoring traffic conditions. The middle level agents coordinate all of the lowest level agents in a subnetwork. The highest-level agent is located in the transportation management center (TMC) to accept human commands and delegate tasks to lower level agents. The re-configurable hybrid control architecture of the system provides the capability of dynamically grouping distributed heterogeneous agents (intelligent control systems) into virtual clusters to accomplish tasks related to different geographical areas and different purposes. A platform independent agent execution engine has been implemented using an embeddable C/C++ interpreter called Ch. The communication between agents that reside on different hosts has been simulated in the Integration Engineering Laboratory at the University of California, Davis. The use of agent technology greatly enhances the distributed computing and cooperation capabilities of traffic detection and management systems.Copyright

Digitally Controlled Optimal Self-Calibration for a Laser-Photodiode Array Based Vehicle Detection System

The Laser-photodiode Based vehicle Detection System (LBDS) is an advanced vehicle detector. Its detection principle is based on projecting laser beams to the road and receiving the echo laser. When the operation environment such as the road surface condition, the weather and the daylight changes, which is likely to happen over the long-term lifespan of the LBDS, the LBDS may require recalibration. To solve this problem, a digitally-controlled optimal self-calibration method for LBDS is presented in the paper. With the calibration, the LBDS has the ability to operate reliably in a wide range of applications, and has the ability to provide correct and accurate detection information over the long term. The field test results of the LBDS using the proposed self-calibration method confirm the effectiveness of the self-calibration method.Copyright

Design of a Mobile Platform for Overhead Detectors for Vehicles on the Highway

The California Department of Transportation, like many such departments in the United States, is working on developing a new family of electronic sensing devices for the purpose of monitoring certain characteristics of road vehicles as they move along the highway. The devices currently under development are to be located overhead individual highway traffic lanes, from where they can have a clear “view” of ground vehicles. In order to deploy these devices, there is a need to develop the capability to safely and efficiently mount them above highway traffic lanes, using existing overhead bridges and sign structures as support structures. This paper presents a technical study of a universal support platform for these devices. The study discusses such issues as mobility, reliability, and resistance to environmental and other hazards. Results of tests conducted on a prototype are also presented.Copyright

Control of a Mobile Support Platform for Vehicle Detectors on Highway

The California Department of Transportation has sponsored the development of a new family of out of pavement, laser based sensing devices for monitoring road vehicles on the highway. These devices are to be placed over highway traffic lanes, so that they can have an unobstructed view of vehicles moving along the highway. It is expected that there will be need for relatively frequent adjustment of the actual location of these devices over the freeway, so that they can be moved from one lane to another, or so the position over a given lane can be modified. Because of these constraints, a mobile support platform is planned for these devices. This paper presents a motion control strategy for such a mobile platform, and the necessary hardware to implement the control system. The ideas presented in the paper have been tested on a prototype mobile support platform.Copyright

Real-Time Architecture for an Electro-Mech-Optical System for Detection of Vehicles on Highway

A real-time architecture for a highway vehicle detection system is presented in the article. The Laser Based Detection System (LBDS), focused on helping the Intelligent Transportation System (ITS), measures a key quantitative parameter of vehicles moving across a link of highway, namely, travel time. Travel time is based upon the identifying and reidentifying vehicles at various points on the highway. This article provides a method to collect real-time signals from an active laser source in the LBDS and calculate vehicle parameters using a standard computer. A method of message exchange between a real-time kernel process, for real-time data acquisition, and a user space process, for computing and displaying, is given under the RTLinux environment. Experimental results from field tests have shown that the application of the real-time architecture to the LBDS provides speeds deterministically.Copyright