Research Areas

1Network Dynamics and Control
Many networks suffer from costly instability problems where amplification of minor operational disturbances leads to drastically inferior system performance (e.g., causing extra delay and resource consumption). For example, in supply chains where suppliers act independently and place orders from their neighbors based on inventory and sales information, experience shows that fluctuations in order size over time are usually greater for suppliers that are farther away from the customer demand. In congested traffic, slight vehicle accelerations or decelerations near a bottleneck eventually grow into cyclic stop-and-go patterns upstream. We are interested in developing mathematical models to discover root causes of such systems instability problems and further proposed stabilizing strategies. We present analytical stability conditions for deterministic and linear-time-invariant systems, and then allow for nonlinearity and uncertainty in the operating environment. Our results reveal how key features of a system affect stability, and also suggest how to develop stable operating policies either by sharing information across the system (centralized), or by introducing advance commitments. Internet-based role-playing simulation programs have been developed to verify the effectiveness of various strategies under realistic environments. These research efforts are mainly sponsored by NSF.

Representative publications: J7, J8, J11, J13, J18, J60, J70, C1, C3 (bullwhip effect in supply chains); J19, J31, J34, J60, J84 (traffic oscillation); J101, J106 (bus bunching); J108 (epidemics)
2Logistics and Transit
We develop modeling and solution methods to improve efficiency of complex logistics systems, including topics such as large-scale facility locations, vehicle routing, freight distribution systems at container ports, and railroad yards, through a combination of techniques such as approximation, relaxation, and decomposition. For example, we propose an algorithm that translates the "continuum approximation" (CA) recipes for location problems into discrete designs. A simple discretizing process is illustrated here. In projects sponsored by AAR and CSX Transportation, Inc., we develop network design models for the placement of service facilities in railroad networks to ensure the health and performance of locomotives and railcars. Other topics include transit network planning and operations, reliable facility location design under probabilistic disruptions, and large-scale scheduling for maintenance crew.

Representative publications: J20, J21, J32, J44, J45, J71, J102, J105 (supply chain network under disruptions); J22, J27, J64, J89, J92, J98, J99 (fleet scheduling, routing, fueling, and pricing); J35, J58, B3 (transit network design); J104, J107, J112, J114, J115 (shared mobility); J9, J10, J39, J42, J57, J59, J67, J72, J73, J82, J85 (logistics systems design), J14, J40, J49, J56, J87, J100 (railroad operations); J30, J48, J75 (disaster relief)
3Sustainable and Resilient Infrastructure Systems
While the urban infrastructure is aging, the need for optimal management strategies to allocate limited resources for interdependent infrastructure retrofit and maintenance is pressing. We present mathematical programs, analytical models and solution algorithms for planning infrastructure management activities. We have also studied sustainability, resilience and robustness of a system of infrastructure systems (e.g., transportation, agricultural, hydrological, ecological, socio-economic systems) in the contexts of the fast-growing bio-energy production industry and the post-harvest food supply industry. We hosted the Third NSF EFRI-RESIN Workshop on Modeling Sustainable, Resilient, and Robust Infrastructure Systems. More recently we have been collaborating with researchers at USACE to develop analytical and simulation models that help improve military logistics systems and critical infrastructure protection against cascading disruptions in hostile environments. We have also investigated impacts of freight logistics activities on regional and urban air quality, global climate change, and environmental sustainability.

Representative publications: J5, J6, J36, J57, J63, J93 (pavement management); J33, J55, J66, J78, J79, J91, J103, C2, C4, C5, C6 (energy and transportation sustainability); J43, J97, C7 (infrastructure systems resilience)
4Traffic Operations and Surveillance
We have developed data mining, anomaly detection, and pattern recognition algorithms for traffic surveillance and management on large-scale highway and railroad networks. In addition to using nonlinear system dynamics techniques to model traffic oscillations under complex car-following laws (see Research Area 1 above), we have explored impacts of next-generation transportation techniques (e.g., intelligent vehicles) and optimal ways to deploy sensors for surveillance. The work in this area is mainly supported by NSF.

Representative publications: J28, J41, J90, J96 (traffic operations); J17, J23, J38, J88 (sensor deployment)
5Transportation Safety
We account for simultaneity of injury severity outcomes in multi-vehicle collisions. This was done by presenting a simultaneous logit model of endogenous interrelationships among injury severities in multi-vehicle collisions. The methodology provides for unbiased estimators and efficiency gain when correlation between injury severities is high, and can naturally be extended to multiple severity categories in multiple-vehicle collisions. We have collaborated closely with IDOT through several research projects to improve safety on Illinois highways and local roads. We have also hosted the 2009 National Safety Performance Function Summit, the 2010 Highway Safety Manual Lead State Peer to Peer Workshop, and the 2012 National State Safety Engineers and Traffic Engineers Peer to Peer Workshop.

Representative publications: J4, J16, J25


We gratefully acknowledge research support from the following sponsors.
*U.S. National Science Foundation (NSF)
*U.S. Environmental Protection Agency (EPA)
*US Army Corps of Engineers (USACE), Construction Engineering Research Laboratory (CERL)
*CSX Transportation, Inc.
*BNSF Railway, Inc.
*USDOT Region V Regional University Transportation Center
*Illinois State Toll Highway Authority
*Illinois Department of Transportation (IDOT)
*California Air Resources Board (CARB)
*Lake County Division of Transportation
*ADM Institute, ADM Company
*Illinois Campus Research Board
*Illinois Strategic International Partnerships (ISIP)
*CEE@UIUC Innovation Grant Program
*Institute for Sustainability, Energy, and Environment (iSEE), UIUC
*Association of American Railroads (AAR)
*Energy Biosciences Institute (EBI), BP Inc.
*CRRC Institute, China
*ZJU-UIUC Institute Research Program