Welcome to the Prof. Taek Kwon's Research Page

This page is intended to provide a brief overview of my current research work at UMD. Unfortunately, it seems I could never find enough time to construct a good web page that I wish to provide. It will be always partial, but if anyone is interested in my research beyond what is available here, I am willing to provide more informaiton. So please don't hesitate to contact me at 218-726-8211 or email me at tkwon@d.umn.edu.

Selected Research Reports

Rare Papers frequently requested

My Recent Research Projects:

Develepment And Evaluation Of An Advanced LED Warning System For Rural Intersections

In Minnesota, 70 percent of all intersection-related fatal crashes for the period of 2006 to 2008 occurred at rural, through/stop intersections. The Minnesota Department of Transportation (Mn/DOT) identified improving the design and operation of intersections as a critical emphasis area in the Minnesota Comprehensive Highway Safety Plan. At these intersections, sight restrictions caused by vertical and horizontal curves negatively affect a driver’s ability to safely accept a gap in the traffic stream. This paper presents the result of a two year study on the development of a new intersection warning system referred to as an Advanced Light Emitting Diode (LED) Warning System (ALWS) and evaluation of the system’s effectiveness. The ALWS was developed to address the sight restrictions in rural through/stop intersections, and it consists of vehicle detectors that detect approaching or stopped vehicles and LED warning signs that respond according to the received messages from the detectors. The warning signs have LEDs on the perimeter of the sign and a warning message in the middle, which is commonly referred to as a blinker sign. All signs and detectors are powered by solar panels and rechargeable batteries. All message communications between the detectors and warning signs are performed through wireless transceivers. In order to evaluate this new warning sign technology, the system was installed at the intersection of West Tischer Road and Eagle Lake Road in Duluth, Minnesota. Video data was collected through an on-site video monitoring system consisting of a Digital Video Recorder (DVR) and two video cameras. The first camera records video of vehicles traveling towards the intersection through the vertical curve. The second camera records vehicles traveling through the intersection. In addition to video data collection, mail-in and on-site surveys were conducted. Overall, the ALWS was effective at reducing vehicle speeds on the main approach, and increasing the wait time and altogether stopping roll-throughs for vehicles on the minor approaches when a conflict exists at the intersection. However, an increase in roll-throughs when no conflict exists at the intersection was observed, which must be addressed in the future design of the ALWS. According to the mail-in and on-site survey results, 80 percent of respondents expressed that the warning system is effective. If the increase in roll-throughs under no conflict conditions can be addressed, the researchers conclude that the ALWS is an effective system for reducing crashes in rural stop/through intersections.
Video Demo: ALERT-1 Sign.

Development of a Weigh-Pad Based Portable WIM System

Weigh-in-Motion (WIM) systems produce individual vehicle records of traffic information that includes lane number, time-stamp, speed, axle loads, axle spacing, and classification of the vehicle type. This detailed traffic information has been used in a wide range of applications, i.e., pavement analysis and design, overweight enforcements, traffic data analysis and reporting, freight estimation, traffic monitoring, etc. Although benefits of WIM data are evident, initial construction and the subsequent maintenance of permanent roadside WIM stations are expensive. WIM stations, therefore, have mainly been installed on roadways with heavy traffic, such as interstate and trunk highways. They are almost nonexistent on rural local roads because of low Average Daily Traffic (ADT) and difficulty of cost justification. However, low ADT on rural roads does not mean fewer overweight violations, or diminish needs for protecting the roads from overweight vehicles. Heavy truck volumes on local roads, indeed, have been increasing, caused by higher demands on agricultural commodities. This raises a grave concern for many local transportation engineers, because it could significantly shorten the life of local roadways. To monitor road wear or to protect from overweight vehicles, traffic engineers need to know the truck volumes and weights but without the cost of permanent roadside WIM stations.
One solution to bring WIM technology to local roads is to utilize a portable WIM system, much like pneumatic tube counters used in short-duration traffic counts. That is, a single unit is reused in multiple locations for few days at a time. This way, WIM data is obtained without the cost of a permanent WIM station. Unfortunately, WIM development efforts have mainly been given to in-pavement permanent systems; consequently, portable WIM systems are not available on the market. This report describes the results of a two-year research project sponsored by the Minnesota Department of Transportation (MnDOT) to develop a portable WIM system that can be readily deployed on local roads.
The objective of this project was to develop a portable WIM system that would be used much like a pneumatic tube counter. The sensor chosen was the RoadTrax BL sensor strip (or simply “BL sensor”), which is a thin, narrow piezoelectric strip. To accomplish the project objective, the BL sensor strips were sandwiched and glued between two strong conveyer belts. Conveyer belts provide flexibility and durability needed for on-pavement installations. A standard sensor constructed has a length of 24 ft covering two lanes of roads and a width of 1 ft. This new sensor is called a “weigh-pad.” The final completed system is called a weigh-pad system and consists of a pair of weigh-pads and a console computer. For installation, two weigh-pads are laid across the traffic lane separated by a known distance (typically 12 to 16 ft) and fastened on the pavement surface using sleeve anchor screws. The edges are then taped using strong-bonding utility tapes. Since on-pavement installations produce much stronger charge signals than in-pavement installations, a customized charge amp was developed to handle the different charge responses. In addition, a durable, field-ready enclosure that houses all necessary electronic components and a computing unit was designed and fabricated. The final system consists of two parts, a console box and a pair of weigh-pads, and is truly portable. One of the advantages of the weigh-pad system is that sensor installation does not cut into the pavement. Since the installation does not weaken the pavement structure, it would be safe to use on structurally sensitive areas such as on bridge decks.
To verify WIM capabilities of the weigh-pad system, driving tests were conducted at the MnRoad facility and also from the Minnesota Trunk Highway 53 (TH-53). Two types of effects were tested at MnRoad, which are the effects of temperature and speed to the weight measurements. For temperature tests, a single test vehicle with a known weight was driven over the weigh-pads repeatedly in the pavement temperature range, 85 - 135 ºF, and the corresponding gross vehicle weights (GVWs) translated from the axle waveforms were analyzed. The expected trend was for the GVW to increase as the pavement temperature rose, since heat increases charge production of the piezoelectric sensors, but the data did not show any trend. This outcome is mainly attributed to the charge amp design in which it filters out any signal components that have a period longer than 20 sec. Pavement temperatures, in general, change over a longer time period, such as in the order 10s of minutes, which are clearly outside the 20 sec time constant. Consequently, most charge signals generated by the pavement heat must have been drained from the charge amp.
The next test was speed effect on vehicle weight. Since weigh-pads are installed on the surface of the pavement by fastening the pads, they are slightly extruded. When a vehicle drives over the installed weigh-pads, a sound of hitting a small bump can be clearly heard. This bumping sound becomes louder as the vehicle speed increases. This begs the question: Does the vehicle speed affect the vehicle weight measurements? To answer this question, the same test vehicle was driven multiple times at speeds close to 10, 20, 30, 40, 50, 60, 70, and 80 mph, and the corresponding weights were analyzed. The data showed an increasing trend of weights as the speed increased. This result explains the bigger bumping sound as the vehicle speed increases and suggests that there is a need for a calibration of the measured weight with respect to the vehicle speed.
The final tests were conducted at an existing in-pavement WIM site for a side-by-side comparison. The chosen road was one of the Minnesota trunk highways and had an average traffic speed of about 70 mph. The weigh-pads were installed right next to a WIM site constructed using Kistler Lineas quartz sensors and an IRD iSync WIM system. A total of 3,235 vehicle records were compared for three parameters: GVW, speed, and axle spacing. Normalized Root Mean Square Errors (NRMSEs) between two systems on GVW, speed, and axle spacing were 3.88%, 2.22%, and 0.5%, respectively. Correlation coefficients between two systems for GVW, speed, and axle spacing were 0.97, 0.97, and 0.99, respectively. The coefficient of determinations, denoted as R2, were 0.93, 0.93, and 0.99 for GVW, speed, and axle spacing, respectively. Lastly, the difference in vehicle classifications between the two systems was merely 1.5%. All of the comparison measures indicate that the WIM data obtained by the weigh-pad system is only a few percentage points different than the data of the same traffic obtained by a permanent in-pavement WIM system. This test result suggests that the weigh-pad system developed in this project provides WIM data with a quality similar to that of a permanent in-pavement WIM system.
In conclusion, this project successfully demonstrated that a reusable, portable WIM system that would work much like a pneumatic tube counter can be built and deployed. A side-by-side comparison verified that the data quality difference between the portable on-pavement and a permanent in-pavement system is minute. With few improvements, the researchers believe that the weigh-pad system is a solution for bringing the WIM technology to local roads at a low cost.

Video Presentation Produced by MnDOT

Cellular Wireless Mesh Sensor Network for Vehicle Tracking in an Intersection

Automatic vehicle tracking has been one of the challenges in traffic detection technologies. Video cameras and radars had only limited success in part due to the problems with occlusion, land object noises, weather, and high computational and physical costs. This research project involves the development of a reliable cellular wireless mesh sensor network (WMSN), utilizing recent advances in ZigBee technology. The WMSN is self-constructing, self-healing, and can support a large number of nodes. Each node of the WMSN has a minimum footprint that consists of a microcontroller with a radio frequency transceiver, an anisotropic magnetoresistance sensor for detecting vehicles, and a lithium-ion rechargeable battery. A node is placed in each lane of the intersection to form a WMSN. A separate node is responsible for collecting and logging the data from each node in the network. From this logged data, a vehicle tracking algorithm analyzes the logged intersection data and tracks the trajectories of the vehicles through the intersection. Actual intersection data was collected and successfully tracked using the vehicle tracking algorithm with an average of over 90 percent accuracy. Final Report: Portable Cellular Wireless Mesh Sensor Network for Vehicle Tracking in an Intersection

Development of a PC-Based Eight-Channel WIM System

Weigh-in-Motion (WIM) data provides vital information for pavement design and maintenance. The purpose of this research project was to improve the present piezoelectric WIM technologies through a better system design and signal processing algorithms. Present WIM systems are only available as proprietary systems, i.e., the internal system design and algorithms are highly guarded making it difficult to compare and improve the underlying technology. Therefore, the second objective was to develop a WIM system based on an open architecture, utilizing a standard PC and off-the-shelf components, and to publish the details of the design to promote an open architecture for continuous future improvements by other developers. The research team was able to successfully develop a working eight-channel WIM system, and the details are described in this report. The main innovation introduced in this research is a hardware-in-the-loop (HIL) WIM simulator that can generate analog axle and loop signals through software control. The HIL simulator can create ideal axle signals, as well as erroneous signal conditions, that can be directly fed into WIM systems. The main advantage of using a WIM HIL simulator for developing a WIM system is that the developers may run an unlimited number of signal tests without actually driving a single vehicle through the WIM sensors, thereby significantly reducing the development time and cost. The erroneous signal conditions generated by the HIL simulator can also identify the error handling capabilities of a WIM system. The proposed HIL simulator for WIM system development is new and provides an elegant solution to the unavailability of an ideal axle signal.

Visibility Measurement System Based on Imaging Technologies

This research project focuses on developing a practical atmospheric-visibility monitoring system based on imaging systems. Because visibility reductions due to inclement weather conditions are one of the main causes of traffic incidents, and among one of the primary criteria used to determine road closures in winter, accurate visibility measurement is prime importance to many transportation decision makers. However, accurate and reliable measurement of atmospheric visibility is challenging because it continuously changes over time and space and is influenced by a host of atmospheric conditions such as fog, rain, snow, smog, dust, sun direction, solar radiation, etc. Measurement by human observers is often unreliable due to differences in individual eyesight, perception and other biological conditions. Other techniques such as light-scatter meters exist, but do not measure the true visibility. A new approach developed in this research is based on the measurement of visibility through an imaging system that comprises a surveillance video camera, an image digitizer and multiple targets positioned at specific distances from the camera. For daytime, an image-processing algorithm was developed to determine at what distance the foreground is no longer distinguishable, by which the distance represents the visibility. For night visibility, several approaches are under investigation. Those include embedding light sources in the targets with the frequency range in visual and infrared spectrum and using different types of spectral filters in the camera. We also investigate a new way of measuring visibility based on the concept of relativity. This research was sponsored by USDOT and Mn/DOT.
Click here to see a daytime visibility screen of the system.
Click here to see a night visibility screen of the system.
Final report Phase-1: Atmospheric Visibility Measurements Using Video Cameras
Final report Phase-2: Atmospheric Visibility Measurements Using Video Cameras: Relative Visibility

The following areas of research are also under way.

Non-Uniform Image Processing

Most of the techniques employed in the area of image processing have been explored by uniform processing approaches in its nature. For example, image compression uniformly compresses all areas of the image without regarding such as the human perception of objects in the image (which may provide critical information on "which portion of the image is more interested or important than others"). Another such area is in image interpolation. Most interpolation techniques apply one formulation or another without knowing how much distortion would be caused to the image as a result of this uniform formulation of the interpolation algorithm, which essentially leads to introducing many blocky effects. The effect on the Fourier Transform is a non-issue and at times it is very cumbersome to find the effects of these arbitrary interpolation techniques on the frequency domain. This creats havoc on the frequency components. A better and sensible approach is associating a non-uniform processing based on human perception. My research effort is to develop a non-uniform image processing that accounts human perception in particular for image compression and interpolation.

Object Recognition

The area of object recognition has traditionally been synonymous with the technique of template matching. However I believe that it is highly unreliable due to some of its inherent characteristics. My effort is to develop a newer technique that can be more generalized in terms of human intelligence and perception. The direction of this research is to follow the simple common-sense concept that we human beings detect or recognize a pattern or an object from a scene by interpreting the syntax of features that make up an object. This approach is incrediably efficient in terms of data as demonstrated by few strokes of cartoon artists. Unfortunately, we know very little about how to automatically extract features and feature-syntax relation from raw data. I am presently in the process of developing few new techiques and applying the algorithm in visibility measurements for the Deaprtment of Transportation.

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