Transportation is such an interdisciplinary field. It draws knowledge from computer science, economies, information theory, and social science. And it makes you feel quite achieved to have an in-depth understanding of the problems that people experience every day and knowing that you are working to find a solution for it.


Xiaoyue Cathy Liu: Beating Rush Hour Traffic

University of Utah Civil & Environmental Engineering Assistant Professor Xiaoyue Cathy Liu wants to make going to work a more pleasant experience. Liu is studying ways public transportation can help decrease traffic congestion and what cities can do to make driving on U.S. highways a less maddening journey.


Q: Why did you choose to work at the University of Utah and what strengths in traffic-related research do you see in the U’s Department of Civil & Environmental Engineering?

A: My Ph.D. dissertation was about modeling managed lanes, i.e. those freeway lanes that are managed in real-time such as the Interstate 15 express lane. A big component of my research was to determine how those toll lanes affect traffic. The I-15 express lane is the longest continuous HOT (High-Occupancy Toll) lane system in the U.S., and I have always been curious about how the system actually functions here in Utah. That was the very first motivation for me to come to Salt Lake.

More importantly, the civil engineering department here provides valuable resources for research. My colleagues are great researchers in their respective fields, and the facilities are top-notch for conducting cutting-edge research. The Utah Traffic Lab here has workstations that are connected to the Utah State and City Traffic Control centers to receive live streaming of surveillance cameras. It also has a state-of-the-art driving simulator to test people’s behavior under a variety of simulated scenarios. The lab has a long-standing relationship with the Utah Department of Transportation, Utah Transit Authority, and the Wasatch Front Regional Council through past research collaborations. This history offers unparalleled opportunities and tremendous support for knowledge sharing, which is really critical for conducting quality research.


Q: How did you become interested in traffic and public transportation as your field of study?

A: My bachelor’s degree is in electronic and electrical engineering, mainly because of my dad who is a great electrical engineer and was a great influence on cultivating my interests in that field. And I was actually about to accept an offer to the Ph.D. program in fiber-optic communication at Peking University in China when I met a professor who talked about the booming field of Intelligent Transportation Systems and how my background in electrical engineering can be well suited for transportation. So I finally decided to take a leap of faith and came to the U.S. to embark on a brand new journey. And I have been into it since.

Transportation is such an interdisciplinary field. It draws knowledge from computer science, economies, information theory, and social science. And it makes you feel quite achieved to have an in-depth understanding of the problems that people experience every day and knowing that you are working to find a solution for it.


Q: What are you researching regarding public transit systems?

A: My research in public transit is to evaluate the transit system performance and use data-driven methods to design a network that promotes multimodal transportation. The rapid growth of public transit systems in the metropolitan areas leaves a lot of research questions unanswered. For example: How do you make transit more “attractive” to people, in particular sensitive populations? How do you coordinate with the traffic signals so buses can arrive at each stop on time? How do you balance among the interplay of operational efficiency (cost vs. ridership), spatial equity, and service quality?


Q: You are conducting research on shared mobility services such as bikeshare initiatives. How can we improve on them and how is the one in Salt Lake City — known as GREENbike — working for residents?

A: Shared mobility services (bikeshare and carshare), if designed properly, can extend the reach of public transit service, which offers a great opportunity for solving the transit “first mile, last mile” problem. Such co-location design at transit hubs can significantly enhance people’s travel options, help reduce parking and congestion at stations, and promote a healthy and environmentally-friendly lifestyle.

GREENbike is just such a shared mobility program here in downtown Salt Lake. It provides different types of memberships to suit users’ needs and offers people with short-term, one-way access to bikes parked at certain locations

The program has been working quite well for the residents. We have seen a significant increase of trips since its expansion in 2014. We are currently working with GREENbike to conduct travel behavior analytics. Using the GPS data for each bike rental transaction, we developed a map-matching algorithm and successfully characterized roadways through network topology modeling. We also applied a discrete space location-allocation model for new bike rental station expansion.


Q: Traffic along the Wasatch Front fares well nationally against other large urban areas but will continue to worsen as the area grows and building projects and road projects increase with that growth. What can be done to help curb the potential rise in traffic congestion?

A: There are several ways to combat congestion that transportation professionals are working on. The multimodal transportation network I mentioned earlier is one important component. Meanwhile, through the use of advanced technologies, our roads are getting smarter in proactively responding to congestion. Ramp metering, adaptive signal control, and high-occupancy toll lanes (I-15 express lane) are some of the proven strategies that are effective in alleviating congestion. Also, the concept of V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure) and autonomous vehicles are gaining more and more attention and popularity. These technologies will allow vehicles to talk to each other and talk to infrastructure through wireless exchanging of data so people can get to where they need to quicker and safer.


Q: What can people do to help improve their experience commuting from home to work if they drive?

A: UDOT has a very handy app developed called UDOT Traffic that not only provides users with real-time information of road conditions — including incidents, work zones and surveillance camera images — but also forecasts traffic conditions built upon models and historical data.

For commuting to work, we have a concept called “peak spreading.” One contributing factor to this phenomenon is that some people choose to avoid congestion during peak periods by starting their work trips earlier or later. If flexible work schedule allows, this could be one feasible solution. For people that have a fixed work schedule, purchasing a transponder to use the toll lanes (e.g. I-15 express) is also an option. However, my best suggestion is always to encourage people to carpool for better to improve the air quality. The biggest advantage of carpooling is being able to use the HOV express lane for free, which offers a better travel experience.