• Journal of Korean Society of Transportation
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• v.28 no.5
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• pp.141-153
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• 2010

The study is about the development of operating speed prediction models aimed for an evaluation of design consistency of four lane rural roads. The main differences of this study relative to previous research are the method of data collection and classification of road alignments. The previous studies collected speed data at several points in the horizontal curve and approaching tangent. This method of collection is based on the assumption that acceleration and deceleration only occurs at horizontal tangents and the speed is kept constant at horizontal curves. However, this assumption leads to an unreliable speed estimation, so drivers' behavior is not well represented. Contrary to the previous approach, speed data were collected with one and data analysis using a speed profile is made for data selection before building final models. A total of six speed prediction models were made according to the combination of horizontal and vertical alignments. The study predicts that the speed data analysis and selection for model building employed in this study can improve the prediction accuracy of models and be useful to analyze drivers' speed behavior in a more detailed way. Furthermore, it is expected that the operating speed prediction models can help complement the current design-speed-based guidelines, so more benefits to drivers as real road users, rather than engineers or decision makers, can be achieved.

• International Journal of Highway Engineering
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• v.14 no.2
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• pp.73-81
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• 2012

The bicycle is an environment-friendly transport mode leading to a more sustainable transportation system. To innovatively increase the use of bicycle as a significant transport mode, bicycling-friendly roadway environment should be provided. From this perspective, the scientific and effective assessment of roadway environment in term of the bicyclist perception for safety and comfortability is of keen interest. This study develops a methodology for evaluation cycling environment using probe bicycles. A global positioning system(GPS) based speedometer was used to collect bicycle speed data. Cycling comfortability index(CCI) was derived for the purpose of evaluating cycling environment. The proposed CCI can be effectively used as an assessment tool in the field of bicycle transportation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.767-774
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• 2008

This study has been developed the way that evaluates the road safety using the speed of individual vehicles at curve sections in 2-lane rural highways. For this study, we developed variation of operational speed for the individual vehicle using the speed of vehicles in 96points of selected roads. Drawing out of variation of operational speed for the individual vehicle, estimation models for speed variation of individual vehicles considering horizontal alignments and vertical alignments of the roads have been developed. These models presents the way to evaluate road safety out of the operational speed and acceleration of individual vehicles. Considering safety and based on the results of these study above, some regular spots are ranked by "good", "fair", "bad". The results that this study showed in this paper could be useful to derive some particular spots that needs to be improve in terms of safety.

• Korean Journal of Agricultural Science
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• v.23 no.1
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• pp.138-149
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• 1996

This study was aimed at predicting to running speed related to alignment factors of forest road, and recommending the improvement method of forest road construction using the running speed of vehicles. For these purposes, this study proceeds to select forest roads after reviewing the planning papers and maps, to measure the road alignment factors such as longitudinal gradient, width of roadway, radius of curve, length of curve, superelevation, and conditions of road surface on the subject forest road. It was found that the average running speed of logging truck showed lower value than that of the expected speed of 'Forest Road Construction Regulations and Rules', and the average running speed of loaded truck showed 70-85% of the speed of empty truck. According to the road conditions, speed index (reductive ratio of running speed) was also calculated with respect to radius of curve, longitudinal dradient. The results of the study on the running speed of vehicle subject to the alignment of forest roads make it possible for one to judge the quality of the existed and to be constructed forest roads, to select the structure of forest road to improve the running speed of vehicle on forest road.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.159-166
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• 2009

On freeways, factors inducing traffic accidents consist of two major elements such as driver factors and road environment factors. Research have been done and shown that there would be relationship between design elements such as radius, slopes, superelevations, and observed speeds and accident rates. The present paper confirms that these elements are correlated with accident rates. Furthermore, the paper identifies standard deviation of these elements as the design consistency and compare them with reduction of accident rates. This type of work leads to identify the fact that standard deviations based design consistency are correlated with accident rates. The results of the paper may contribute to encourage the quantified use of design consistency during highway design.

• Journal of Korean Society of Forest Science
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• v.110 no.4
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• pp.622-629
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• 2021

This study analyzed the running speed of logging trucks (25 tons), depending on the structural state of forest roads, on four main forest roads in the national forest management offices in Chuncheon and Hongcheon for trafficability. The speeds for the curved and straight sections were 7.6 km/h and 8.7 km/h, respectively, which were less than the designed speed (20 km/h). Thus, it would be necessary to improve the forest road's structure to fulfill minimum running speed. No significant difference was observed in the running speed by the longitudinal gradient up to 13%, while it was increased at more than 100 m by the distance in the straight section. By the facility's location in the curved section, the running speed was 6.2%-9.3% lower in a ridge than a valley. The running speed was lowest at the internal angles of <90° and at the curved radius of <15 m, respectively. When this radius was less than 15 m, the substandard sections for widening amounts were more than 50%; thus, sufficient widening was not achieved.

• Journal of KIISE:Information Networking
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• v.31 no.4
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• pp.393-404
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• 2004

Recently, mSCTP (Mobile SCTP) has been proposed as a transport layer approach for supporting mobility. mSCTP is based on the ‘multi-homing’ feature of Stream Control Transmission Protocol(SCTP), and utilize the functions to dynamically add or delete IP addresses of end points to or from the existing connectionin order to support mobility. In this paper, we propose a mechanism to determine when to add or delete an W address, utilizing the link layer radio signal strength information in order to enhance the performance of mSCTP We also propose a mechanism for a mobile node to initiate the change of data delivery path based on link layer radio signal strength information. In addition, if it takes long time to acquire new data path, we propose an approach for reducing handover latency. The simulation results show that the performance of proposed transport layer mobility support mechanism is competitive compared to the traditional network layer mobility supporting approach. Especially, when the moving speed of mobile node is fast, it shows better performance than the traditional network layer approaches.

• The KIPS Transactions:PartC
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• v.17C no.3
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• pp.299-306
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• 2010

IPTV and VoIP services are considered as killer applications over Mobile WiMAX network, which provideshigh mobility and data rate. Among those which affect the quality of voice in those services, the jitter buffer or playout buffer can compensate the poor voice quality caused by the packet drop due to frequent route change or differences among routes between service endpoints. In this paper, we analyze the correlation between the sleep interval length and jitter buffer size in order to guarantee a predefined level of voice quality. For this purpose, we present an end-to-end delay model considering additional delay incurred by the WiMAX PSC-II sleep mode and a VoIP service quality requirement based on the delay constraints. Through extensive simulation experiments, we also show that the increase of jitter buffer size may degrade the voice quality since it can introduce additional packet drop in the jitter buffer under WiMAX power saving mode.

• Convergence Security Journal
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• v.16 no.5
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• pp.49-55
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• 2016

Recently mobile service industry has grown very rapidly. In this paper, We investigated the changes in mobile service network as well as security vulnerabilities of network in future 5G mobile service network, too. Recently, there are rapid developement of information and communication and rapid growth of mobile e-business users. Therefore We try to solve security problem on the internet environment which charges from wire internet to wireless internet or wire/wireless internet. Since the wireless mobile environment is limited, researches such as small size, end-to-end and privacy security are performed by many people. In addition, there is a need of internetworking between mobile and IoT services. Wireless Application Protocol has weakness of leaking out information from Gateway which connected wire and wireless communication. As such, We investigate the structure of mobile service network in order to gain security vulnerabilities and insights in this paper.

• Convergence Security Journal
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• v.8 no.2
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• pp.41-50
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• 2008

Recently amount of traffic into the network rapidly increase since multimedia streaming services is generally adopted for application. In addition, various network management systems have been suggested for providing a stable service and QoS guarantee. It is necessary for such systems to have QoS monitoring module in order to evaluate acceptance or violation of QoS requirements by analogizing a state information of each node within network. In this paper, we suggest a network management system to evaluate QoS level between end-to-end agents and analysis traffics transmitted between them. The proposed system is implemented for the purpose of collecting network traffic information and monitoring of the view. The proposed system makes user easily understand information of QoS parameters such as throughput, delay and jitter by adopting a method of visual and numerical representation. To achieve this, we purportedly generate test packet into network for confirming acceptance or violation of QoS requirements from point of view of multimedia application service.