Welcome 歡迎

I am a Sr. Research Associate in the Department of Mechanical Engineering at the University of Minnesota, Twin Cities campus. I conduct research on intelligent transportation related topics using advanced sensing, embedded computing, and wireless communications technologies for accessible transportation and roadway safety applications. I developed a mobile accessible pedestrian signal (MAPS) system to help the visually impaired navigate street and intersection crossings. I also developed an in-vehicle workzone warning system to alert motorists approaching work zones. My PhD dissertation rececived the "Milton Pikarsky Memorial Award" in science and technology area from the Council of Universities Transportation Center (CUTC).
Previously, I developed ITS interdisciplinary initiatives for undergraduate and graduate courses. I developed several web-based educational modules using the Java™ technology for transportation-related courses in the departments of Civil Environmental and Geo- Engineering (CEGE) and Mechanical Engineering (ME).
My other research activities and interests include: driver assist system (DAS), connected and autonomous vehicle, accessible and assistive systems for people with vision impairment (intersection, work zone), data systems and performance analysis, incident decision support systems, transportation accessibility, transit performance analysis and modeling, adaptive signal priority strategies, and others.


Investigating inductive loop signature technology for vehicle classification counts

This project aims to evaluate the accuracy and reliability of using the single loop detector signature for vehicle classification under different traffic conditions. We believe, there are opportunities to convert current traffic volume counters (ATR/volume) into volume and classification stations using existing inductive loop detectors. The technology has the potential to save lots of time and money, and could provide MnDOT more data especially in the metro area where loop detectors are already installed on freeways, ramps, and at traffic signals. The objectives of this proposal are to, (1) leverage existing loop detectors for vehicle classification counts, (2) if successful, the technology can save lots of time and money, and could provide State, County or City more data especially in the metro area where loop detectors are already installed.

Measure Truck Delay and Reliability at Corridor Level

This project will leverage our previous development to implement the performance measures using the National Performance Measurement Research Dataset (NPMRDS) from USDOT. We will work with stakeholders to select key freight corridors with recurring congestion in peak periods in TCMA. We will use the monthly NPMRDS data to measure travel time reliability and estimate truck delay at corridor level and to identify system impediments during peak hours. The objective is to use performance measures for assessing impact of truck congestions and identifying operational bottlenecks or physical constraints. Trucking activity nearby a congested area will be further examined to analyze traffic pattern and investigate possible causes of recurring congestions. Recommendations for potential mitigation solutions will also be developed to improve system performance for all users.

Using Bluetooth Low Energy (BLE) Technology to Trigger In-Vehicle Messages at Work Zones

This project will examine an inexpensive new technology based on Bluetooth Low Energy (BLE) tags that can be deployed in or ahead of work zones. These can trigger spoken and contextual messages in existing smartphones located in vehicles passing by the tag. Such messages can be updated remotely in real time and as such may provide significantly improved awareness about dynamic conditions at the work zones such as: awareness of workers on site, changing traffic conditions, or hazards in the environment. Key technical issues that will need to be addressed are: What is the maximum Bluetooth scanning rate on a smartphone? What is the Bluetooth and data communication latency? What is the power consumption on smartphone and Bluetooth tags? What is the repeatability of Bluetooth communication at high speed? What is the Bluetooth signal attenuation in different environments? How can such a smartphone app be activated requiring no intervention by the driver?

Kare11 News, 5/25/2017

A Positioning and Mapping Methodology Using Bluetooth and Smartphone Technologies

Commercially available BLE tags, primarily designed to be detected or discovered, do not communicate with each other. This project aims to develop a standalone Bluetooth smart system (called BLE-smart) that integrates a commercial off-the-shelf BLE module operating in dual modes (master/slave or scanning/advertising) with necessary interface elements to sense other BLE-smart devices within its range of communication. A positioning and mapping algorithm will be developed to create a local map of an unfamiliar or hazardous environment. The BLE-smart units will remember and check the other BLE-smart devices in their communication range to ensure the integrity of the local map and to provide correct positioning information in GPS-denied environments. A geospatial database that contains the location and corresponding message of each BLE device will be integrated with a smartphone app. The goal is to provide reliable situation awareness and corresponding navigation information to assist wayfinding for the visually impaired. The mapping methodology is to ensure that correct audible information (such as signal timing and intersection geometry) is provided to users at the correct location.

Implementation of Traffic Data Quality Verification for Weigh-in-Motion Sites

An implementation guideline for WIM sensor calibration was developed. A mixture modelling technique using Expectation Maximization (EM) algorithm was developed to divide the vehicle class 9 Gross Vehicle Weight (GVW) into three normally distributed components, unloaded, partially loaded, and fully loaded trucks. A popular statistical process control technique, Cumulative Sum (CUSUM) was performed on daily mean GVW estimates for fully loaded class 9 vehicles to identify and estimate any shift in the WIM sensor. Special attention was given when presence of auto-correlation in the data was detected by fitting time series model and then performing CUSUM analysis on the fitted residuals. Results from the analysis suggested that the proposed methodology was able to estimate shift in the WIM sensor accurately and also indicated the time point when the system went out-of-calibration. A data analysis software tool, WIM Data Analyst, was developed based on the Microsoft Windows .NET framework. An open source software tool called R.NET was integrated into the .NET framework to interface with the R software which is another open source software package for statistical computing and analysis.

Using Truck GPS Data for Freight Performance Analysis

This research studied the surface freight performance in the Twin Cities metropolitan area (TCMA) using commercial GPS data from private industry and existing Automatic Traffic Recorder, Weigh-In-Motion, and loop detector data from MnDOT. The objectives of this study are to integrate private and public freight data sources to generate freight mobility and reliability measures and to identify significant freight node and corridors in the Twin Cities metro area (TCMA). The outcome will allow freight agencies to: (1) better identify system impediments such as traffic congestion or truck bottlenecks; (2) investigate truck volume contributing to traffic congestion and delay; and (3) use the derived measure as a guide for decision support on infrastructure investment, freight forecasting, and planning.

Use Smartphone App to Help the Visually Impaired Navigate Work Zones Safely

People who are visually impaired often encounter physical barriers that limit their accessibility and mobility. Building upon our previous study on providing geometry and signal timing to the visually impaired at signalized intersections, this project will investigate what types of information are helpful in providing bypass or routing instructions and develop a smartphone-based auditory navigation system to assist the visually impaired pedestrians in navigating work zones safely.

KSTP News (2/18/2015)

Mobile Accessible Pedestrian Signals for the Visually Impaired

The blind and visually impaired usually walk or use public transit as their primary mode of transportation for pursuing their daily activities. Due to obvious differences in spatial perception as compared to sighted people, they may encounter potential barriers both physically and mentally. This can occur not only for travel in unfamiliar areas but even in familiar areas. Movement barriers may be seem simple and trivial for sighted person to navigate. However, these obstacles create additional challenges for the blind to find their way and thus further limit their transportation accessibility and mobility.
Current Accessible Pedestrian Signal (APS) system required the blind to search for a vibrotactile pushbutton, if one even exists. It often requires the pedestrian to move away from their path of travel, which is often used as an alignment cue for crossing. Due to the high cost of the APS installation, most agencies do not deploy them at all signalized intersections. In addition to the installation and maintenance costs which accrue to the local traffic agency, current APS systems contribute significant "noise" to the local neighborhood. Furthermore, the auditory guiding cues provided by the APS are often inaudible because of the ambient traffic noise associated with rush hour. There is significant room for improvement in terms of the design and accessibility of both APS and non-APS crosswalk signals for pedestrians with vision impairment.

Kare11 News, 2/17/2012

12 News, 4/20/2012

University of Minnesota, ITS Institute, 7/23/2012

University of Minnesota, ITS Institute (with visual descriptions), 9/14/2012

Impact of TSP on Bus Service Performance

As a component of the Urban Partnership Agreement (UPA), Minnesota Department of Transportation (MnDOT), Metropolitan Council, and City of Minneapolis have implemented conditional Transit Signal Priority (TSP) strategy along Central Avenue including 27 signalized intersections in the north of Downtown Minneapolis. Transit service performance before and after the TSP deployment was studied. As a result of the TSP deployment, bus schedule was reduced by 2 minutes to take full advantage of the conditional signal priority strategy. Results indicated that the existing TSP implementation improves bus travel time (TT) by about 4-6%.

Transit Performance Analyst

A methodological data-processing framework was developed to process a massive amount of transit data, including vehicle location, passenger count, and electronic fare transactions (Liao & Liu, 2010). A Transit Performance Analyst, resulting from the data-processing methodology, was developed in collaboration with Metro Transit to automate data analysis and visualization. This analyst tool consists of Time Point (TP) level analysis, inter-TP link travel time/speed analysis and route performance analysis.

Freight Performance Analysis

One of the key measures of freight performance on interstate highways in the United States is travel time reliability. This project utilizes the truck location data obtained from ATRI to study the freight activities along I-94/90. Data analysis methodology and data processing procedures were developed. Travel Time Index (TTI), defined as the peak travel time over the free flow travel time, is proposed to measure the level of congestion. Buffer Time Index (BTI), defined as the difference between the 95th percentile travel time and average travel time divided by the average travel time, is used to measure the travel time reliability along the freight corridor. Truck speed, speed variation, truck volume variation, distribution of destinations, stop location, and rest duration derived from each individual trip were also processed and analyzed.

Educational Modules

I currently work with Professor Henry Liu and David Levinson for a Simulating Transportation for Realistic Engineering Education and Training (STREET) project funded by National Science Foundation (NSF). The focus of the STREET project is to develop and fine-tune a suite of simulation programs that can be easily incorporated in the undergraduate courses.

We have developed and tested in the classroom for the following simulation modules, namely, ROAD: Roadway Online Application for Design, ADAM: Agent-based Demand and Assignment Model, SONG: Simulator of Network Growth, and OASIS: Online Application of Signalized Intersection Simulation. All simulation programs are web-based, which enable easy access and learning outside the classroom. It is noteworthy that commercial transportation simulation packages do exist. The commercial tools designed for professionals, however, are usually complicated and expensive, and thus inappropriate for classroom use, particular in the introductory course which focusing on conceptual understanding. We do not intend to duplicate or even compete with the commercial packages. Our emphasis is to provide a simple web-based simulation tool that allows student to better understand the underlying theory in transportation engineering.

In addition to the undergraduate curriculum development, five lessons and other activities were developed for high school students by David Glick based on the "Traffic Control Game", an animated intersection traffic simulation I developed. ITS Institute piloted the lessons in July 2008, during three of the four weeks of Exploring Careers in Engineering & Physical Science (ECEPS), a summer camp experience for high school students that is a program of the Institute of Technology Center for Educational Programs (ITCEP) at the University of Minnesota. The implementation and evaluation report is available here.

An enhanced version of the traffic control game, called Gridlock Buster, was recently developed by ITS institute through contract with Web Courseworks based on features and ideas from my Traffic Control Game. The Gridlock Buster game was introduced to help high school students better understand traffic management concepts and raise awareness of challenges in traffic engineering. Students were asked to explore and play the game with a goal to obtain highest score by optimizing network throughput and vehicle delay and queue. After playing the game, students were asked in groups to develop hypothesis and conduct controlled experiments using the simulation module mentioed above.

Route Optimization for Understanding Transportation Engineering (ROUTE) is developed based on Glen Koorey's approach (Getting from A to B: Using an Interactive Display to Demonstrate Transportation Planning and Design Issues) presented in 2009 TRB annual meeting. He developed a transportation board display with a landscape that allows students to place magnetic road segments for optimal route design. Based on the origin and destination and initial alignment, students can place linear or curved road segment on the board display to form a roadway along a desired path with different objective, for example, to minimize the user cost, construction cost, or both combined.
This online route optimization game is more flexible and includes additional features that will allow users to select different landscape map, origin and destination locations, and initial direction of alignments.

Wireless Transit Signal Priority

Combining newly available technologies such as onboard Automatic Vehicle Location (AVL)-Global Positioning System (GPS), wireless communications and advanced traffic signal control systems, We have developed a Transit Signal Priority (TSP) prototype system that will subtly adjust the operation of traffic signals along bus routes so that buses carrying passengers receive fewer red signals--with minimal disruption to other traffic. In our previous research project, We evaluated the performance of DSRC versus Wi-Fi network and developed wireless communication prototype using commercial off-the-shelf (COTS) embedded systems. The adaptive TSP strategy based on the AVL-GPS and wireless technology was implemented and validated at an intersection in City of Minneapolis. The next phase study is to deploy the developed systems to several intersections along an arterial to evaluate the impact and benefit of the wireless-based signal priority algorithm and validate the capacity of wireless communication network.