이청원 교수

A model was developed for the location of rapid charging stations for electric vehicles (EVs) in urban areas, taking into account the batteries’ state of charge and users’ charging and traveling behaviors. EVs are one means of preparing for the energy crisis and of reducing greenhouse gas emissions. To help relieve range anxiety, an adequate number of EV charging stations must be constructed. Rapid charging stations are needed in urban areas because there is inadequate space for slow-charging eq

The nonconvex combined traffic signal control and traffic assignment problem is examined using four different algorithms and four example networks. The heuristic iterative approach has been widely used (1) without any justification regarding solution quality and (2) without any treatment of the problem of nonconvexity. This is the first study designed recognizing the nonconvexity of the combined problem and examining quality of different algorithm solutions with convergence pattern analysis. Dri

This study explores travelers’ preference for shared micromobility in the context of last-mile travel from shared parking lots to their final destination in the city center. Based on the results of the stated preference experiment and error component logit model incorporating latent variables, we found that the preference for shared micromobility is affected by the uncertainty of availability as well as both travel time and fare. More specifically, our alternative-specific part-worth utility app

In this study, computational simulations and experiments were performed to investigate the mechanical behavior of the aorta wall because of the increasing occurrences of aorta-related diseases. The study focused on the deformation and strength of porcine and healthy human abdominal aortic tissues under uniaxial tensile loading. The experiments for the mechanical behavior of the arterial tissue were conducted using a uniaxial tensile test apparatus to validate the simulation results. In addition,

Traffic safety education was conducted with data from a vehicle-mounted digital tachograph device to promote bus driver awareness of safe driving behavior. The objectives were to evaluate the duration of the effects of traffic safety education on abnormal driving behaviors and to identify the differences in education effects between two driver groups: normal and dangerous. A 9-week tracing survey was conducted for 61 bus drivers. Traffic safety education was administered to individual drivers ac

The aim of this study is to develop safety performance functions reflecting the categorical impact of exposure variables that may vary with freeway segments. A four-step procedure is constructed. It includes clustering analysis, distribution selection, model specification, and model integration. First, clustering analysis is employed to classify freeway segments into three similar groups. A goodness-of-fit test is performed to select suitable distributions for the safety performance functions of

Traffic signal-setting policies and traffic assignment procedures are mutually dependent. The combined signal control and traffic assignment problem deals with this interaction. With the total travel time minimization objective, gradient-based local search methods are implemented. Deterministic user equilibrium is the selected user route choice rule, Webster’s delay curve is the link performance function, and green-time-per-cycle ratios are decision variables. Three solution codes are implemente

The pile-driving method produces considerable noise and vibrations. Hence, an auger-drilled pile method was developed as a low-noise and -vibration substitute. However, this method does not guarantee the bearing capacity of the pile unless some amount of pile-driving is performed. Therefore, the noise and vibration problems cannot be completely solved. In this study, a prebored screw pile method is proposed to solve these problems. In this method, piles are constructed by the rotary penetration

Because travel time reliability and travel time itself are significant to many transportation system users, transportation planners and decision makers should consider travel time reliability as a key performance measure. Values of travel time reliability have most often been determined by estimating route choice models and evaluating the marginal rates of substitution between the costs and travel time variations. However, the most common formulation imposes strong restrictions on taste variatio

Human errors cause approximately 90 percent of traffic accidents, and drivers with risky driving behaviors are involved in about 52 percent of severe traffic crashes. Driver education using driving simulators has been used extensively to obtain a quantitative evaluation of driving behaviors without causing drivers to be at risk for physical injuries. However, since many driver education programs that use simulators have limits on realistic interactions with surrounding vehicles, they are limited