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Chang-Gyun Roh
Smart Mobility Research Center, Department of Future Technology and Convergence Research, Korea Institute of Civil Engineering and Building Technology, Goyang-si 10223, Korea

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Journal article
Published: 15 June 2021 in Applied Sciences
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The purpose of this study is to analyze the effect of heavy vehicles on traffic flow on a two-lane highway. To achieve this goal, data was obtained from piezosensors on the Seoul–Chuncheon Expressway. Analysis of the data showed that, as everyone knows, the average speed of traffic flows decreases as the proportion of heavy vehicles increases. However, not only the speed decreased, but the speed deviation between vehicles decreased. In other words, it was found that within the traffic group that formed the same platoon, individual vehicles were forced to form similar speeds, resulting in a homogeneous rate. This means that heavy vehicles can be included in the traffic stream, reducing the chances of a vehicle-to-vehicle conflict. This kind of influence can be said to explain that heavy vehicles do not necessarily have a negative effect on traffic flow. In this way, we expect to be able to study ways to manage traffic flow by using the effects of low-speed vehicles.

ACS Style

Chang-Gyun Roh; Hyeonmyeong Jeon; Bongsoo Son. Do Heavy Vehicles Always Have a Negative Effect on Traffic Flow? Applied Sciences 2021, 11, 5520 .

AMA Style

Chang-Gyun Roh, Hyeonmyeong Jeon, Bongsoo Son. Do Heavy Vehicles Always Have a Negative Effect on Traffic Flow? Applied Sciences. 2021; 11 (12):5520.

Chicago/Turabian Style

Chang-Gyun Roh; Hyeonmyeong Jeon; Bongsoo Son. 2021. "Do Heavy Vehicles Always Have a Negative Effect on Traffic Flow?" Applied Sciences 11, no. 12: 5520.

Journal article
Published: 17 May 2021 in Sustainability
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Incheon is a major city comprising the metropolitan area around Seoul. However, it ranks the lowest in terms of road extension scale relative to population and number of vehicles. There is extreme traffic congestion and shortages of parking spaces in downtown Incheon, impacting traffic. Alternative policies of the municipal government to address these issues, including road extension and improving public transportation, have not shown results because of the low satisfaction level of the public transportation service and limited transportation mode transfer owing to travel within the metropolitan area. Therefore, to improve the public transportation service, conducting a comprehensive analysis on the current service and improving its quality were deemed necessary. Additionally, adopting a demand response public transportation service was considered. In conjunction, objective and easy-to-use data should be used, so that if anyone repeats the procedure, the same result should be obtained. For this, we propose the simplest process. Thus, to introduce the service, this study presents a decision-making process by establishing a regional prioritizing methodology based on the transportation environment satisfaction level, average access time to major facilities, public transportation competitiveness, personal vehicle demand, and existing public transit routes. To assess the methodology feasibility and conformity, user satisfaction was analyzed in Jung-gu, Incheon. The analysis showed 91% user satisfaction, verifying that the demand response public transportation service was effectively supplied. This analysis process will be useful when applying and expanding new transportation services.

ACS Style

Chang-Gyun Roh; Hyeonmyeong Jeon. Decision-Making Process for Demand Response Public Transportation Service Design—A Case Study in Incheon, Korea. Sustainability 2021, 13, 5574 .

AMA Style

Chang-Gyun Roh, Hyeonmyeong Jeon. Decision-Making Process for Demand Response Public Transportation Service Design—A Case Study in Incheon, Korea. Sustainability. 2021; 13 (10):5574.

Chicago/Turabian Style

Chang-Gyun Roh; Hyeonmyeong Jeon. 2021. "Decision-Making Process for Demand Response Public Transportation Service Design—A Case Study in Incheon, Korea." Sustainability 13, no. 10: 5574.

Journal article
Published: 25 February 2021 in Safety Science
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In this study, to establish the normal gait indices of the elderly in Korea, we analyze the characteristics of their normal gait patterns and establish reference data. The sample group, selected by purposive sampling, comprises 47 male and 41 female Korean elderly in their 70 s and within the standard height and weight range of ±1σ. Moreover, for the purpose of gait comparison, a reference group comprising 15 male and 16 female participants with a standard physique in their 20 s is formed. Their gait motions are imaged during self-selected normal walking on a flat ground. A comparative analysis between the legs, genders, and age groups is conducted using independent t-tests. The results comprise non-normalized and normalized data; statistically significant differences can be observed between the two datasets. In addition, the gait patterns are similar between the legs and there are no significant differences for most of the spatial and temporal variables between genders. However, between age groups, statistically significant differences can be observed for most variables. Compared to the elderly from other countries, the gait patterns of the Korean elderly have a larger cadence and slower gait speed; in addition, there are no gender differences in the gait characteristics and their step and stride lengths are smaller, suggesting more stable gait patterns.

ACS Style

Chang-Gyun Roh; Jinhee Kim. Korean elderly gait reference data: Spatial and temporal characteristics. Safety Science 2021, 138, 105209 .

AMA Style

Chang-Gyun Roh, Jinhee Kim. Korean elderly gait reference data: Spatial and temporal characteristics. Safety Science. 2021; 138 ():105209.

Chicago/Turabian Style

Chang-Gyun Roh; Jinhee Kim. 2021. "Korean elderly gait reference data: Spatial and temporal characteristics." Safety Science 138, no. : 105209.

Journal article
Published: 28 December 2020 in Applied Sciences
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Since the global population is rapidly aging, social interest in the topic is increasing. However, there are not many studies on the elderly who are able to walk on their own, who make up the absolute majority of the total elderly population. Most studies and technological advancements are focused on either the development of assisting devices or on the elderly who use such devices or have a medical history. Therefore, this study analyzed the walks of 31 ordinary individuals of standard physical size and 31 elderly individuals. While there are studies on general gait and walk, there are not many on “maximum walking,” which is associated with a high risk of fall. For this purpose, a motion analysis system and the Ground Reaction Force Plate were used. The results of measuring and analyzing a total of 15 types of kinematic and kinetic variables as targets showed that the elderly experienced a reduced hike in the walking speed by approximately 5% during maximum walking when compared with normal walking. The variables related to balance were measured to be as high as 12%. Considering this, exercise of the elderly should be more focused on reinforcing variables related to balance, and in particular, emphasis should be placed on maintaining balance even when the walking speed increases.

ACS Style

Chang-Gyun Roh. Physical Exercise Goals of the Elderly through the Analysis of Kinetic and Kinematic Variables of Quick Walking—Results of the Koreans Elderly Using a Motion Analysis System. Applied Sciences 2020, 11, 225 .

AMA Style

Chang-Gyun Roh. Physical Exercise Goals of the Elderly through the Analysis of Kinetic and Kinematic Variables of Quick Walking—Results of the Koreans Elderly Using a Motion Analysis System. Applied Sciences. 2020; 11 (1):225.

Chicago/Turabian Style

Chang-Gyun Roh. 2020. "Physical Exercise Goals of the Elderly through the Analysis of Kinetic and Kinematic Variables of Quick Walking—Results of the Koreans Elderly Using a Motion Analysis System." Applied Sciences 11, no. 1: 225.

Letter
Published: 24 November 2020 in Sensors
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Various technologies are being developed to support safe driving. Among them, ADAS, including LDWS, is becoming increasingly common. This driver assistance system aims to create a safe road environment while compensating for the driver’s carelessness. The driver is affected by external environmental factors such as rainfall, snowfall, and bad weather conditions. ADAS is designed to recognize the surrounding situation and enable safe driving by using sensors, but it does not operate normally in bad weather conditions. In this study, we quantitatively measured the effect of bad weather conditions on the actual ADAS function. Additionally, we conducted a vehicle-based driving experiment to suggest an improvement plan for safer driving. In the driving experiment, when the vehicle driving speed was changed in four stages of rainfall, it was confirmed that it affected the View Range value, where the primary variable is the visibility of ADAS. As a result of the analysis, we demonstrated that when the rainfall exceeded a precipitation of 20 mm, the ADAS sensor did not operate, regardless of the vehicle speed. This means that a problem affecting safe driving may occur due to functionality in bad weather situations in which the driver requires ADAS assistance. Therefore, it is necessary to develop a technology that can maintain the minimum ADAS functionality under rainfall conditions and other bad weather conditions.

ACS Style

Chang-Gyun Roh; Jisoo Kim; I-Jeong Im. Letter Analysis of Impact of Rain Conditions on ADAS. Sensors 2020, 20, 6720 .

AMA Style

Chang-Gyun Roh, Jisoo Kim, I-Jeong Im. Letter Analysis of Impact of Rain Conditions on ADAS. Sensors. 2020; 20 (23):6720.

Chicago/Turabian Style

Chang-Gyun Roh; Jisoo Kim; I-Jeong Im. 2020. "Letter Analysis of Impact of Rain Conditions on ADAS." Sensors 20, no. 23: 6720.

Review
Published: 08 July 2020 in Sustainability
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An automated vehicle performs self-driving by utilizing information gathered through sensors attached to the vehicle. Sensor accuracy is thus mentioned as the major technology for enhancing driving safety. However, since urban centers are replete with sections and situations that handicap driving such as sensor recognition limitations and failures, it is necessary to conduct a study that prepares for driving handicaps. As such, this study aims to derive the sections and situations where driving safety is depreciated and review those problems via an analytic hierarchy process (AHP) analysis on driving handicap factors. The analysis result showed that the importance of these handicap situations is high, and it was confirmed that it is necessary to first review off-road sections, environmental factors (heavy rain or snow), merge sections, and sections with poor lane conditions. The result of this research has significance in reviewing road sections and potential situations that require primary verification for securing the driving safety of automated vehicles. It is expected to be utilized in the relevant studies as a basic study.

ACS Style

Chang-Gyun Roh; I-Jeong Im. A Review on Handicap Sections and Situations to Improve Driving Safety of Automated Vehicles. Sustainability 2020, 12, 5509 .

AMA Style

Chang-Gyun Roh, I-Jeong Im. A Review on Handicap Sections and Situations to Improve Driving Safety of Automated Vehicles. Sustainability. 2020; 12 (14):5509.

Chicago/Turabian Style

Chang-Gyun Roh; I-Jeong Im. 2020. "A Review on Handicap Sections and Situations to Improve Driving Safety of Automated Vehicles." Sustainability 12, no. 14: 5509.