My main research interest is developing new methodologies for modeling and analyzing agents’ behavior in networks. The particular focus of applications is on (but not limited to) urban transportation networks, such as congested transport networks, last-mile supply chain networks, pedestrian activity networks, and human-centric city network designs. Please find below more details and selected outputs for each topic (though under construction). The list of publications is available here.
#RouteChoice #DiscreteChoice #GPS #Network #MachineLearning
Route choice models predict which path a given agent takes to travel from a location to another in a network,
and it has been a central topic to transportation planning/engineering and studied in various fields of research.
However, modeling route choices is challenging mainly due to the complex structure of networks.
I have been contributing to the state of the art by developing new methodologies for route choice analysis.
In particular, I am interested in the link-based (Markovian) approach, which does not require path enumeration while modeling stochastic route choice behavior.
Our achievements so far include the developments of model in extraordinary networks,
method to learn behavior from raw GPS trajectories with measurement uncertainty,
and algorithms to capture positive network attributes within a link-based framework.
The proposed method is applicable not only to car networks but also to pedestrian networks, where agents' behavior is more uncertain and are affected by street attractiveness.
#TrafficAssignment #Equilibrium #RouteChoice #Network
Predicting traffic flows in a network is fundamental to transportation network planning and congestion management.
Network traffic assignment is a problem to analyze traffic flow patterns in networks, given the travel demand between different origin-destination (OD) pairs.
This problem is particularly difficult in congested networks, where agents interact with each other.
It is also important to consider the stochasticity (heterogeneity) and dynamics of traffic flows.
I have been working on the developments of (1) analytical and stochastic traffic assignment models, (2) network loading algorithms, and
(3) efficient and accurate solution algorithms to equilibrium (congested) assignment problems.
Our new models and algorithms are tested on various types of networks, such as vehicular, railway, and pedestrian networks (and their combinations),
but the application is not limited to transportation networks.
#Pedestrian #Activity #TimeUse #TimeSpaceNetwork #GPS
Walking is a sustainable transportation mode, and pedestrian activities are key to designs of lively cities. However, pedestrian behavior in networks differs in many ways from other modes of transportation, and thus traditional travel behavior models cannot necessarily be applied to pedestrians directly.
For example, when walking through a network, pedestrians may take a variety of paths in reaction to attractiveness of streets. Such attractiveness may be locally and visually perceived. They can also perform activities on streets more easily, necessitating modeling of sequences of moves and stays.
Focusing on such characteristics of pedestrians, I have been working on the developments of new travel behavior modeling approaches.
The proposed route choice model allows the evaluation of the positive impacts of street attributes on pedestrian willingness to walk,
without restricting paths that pedestrians potentially take.
Moreover, we are working on the development of an integrated model of pedestrian activities in a time-space network.
In this framework, given time-constraint, pedestrians choose time-space paths that integrally include choices of multiple routes, locations and durations of activities, thereby representing a continuous sequence of moves and stays.
#NetworkDesignProblem #TrafficAssignment #Optimization #Pedestrian
Network design is a problem to optimally plan/design the topology and system of a network based on demand, and has been mainly studied for transportation or supply chain networks.
I am employing this network design concept toward sustainable and human-centric cities; more specifically, to design pedestrian-oriented city centers without causing significant negative impacts on car traffic.
Therefore, our approach is to formulate a network design problem in multi-modal networks of vehiclar and pedestrian traffic (and others).
The framework is presented as a bi-level optimization problem,
where the lower-level problem is multi-modal traffic prediction, and the upper-level problem is the network optimization (e.g., decisions on placement of pedestrianized streets or parking capacities).
Thus, it allows the decisions explicitly considering their effects on network behavior and demand.
