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Estimation of Freight Trip Generation Rates based on Commodity Flow Survey in Korea
Park, Minchoul,Sung, Hongmo,Chung, Sungbong The Korean Society for Railway 2012 International Journal of Railway Vol.5 No.4
In Korea, almost 700 industrial parks are under operation. Generally, industrial parks consist of national industrial parks and local industrial parks which are managed by a central government and by local governments respectively. The developing countries such as Korea, China and Vietnam etc. have constructed many industrial parks, which result in the change of land use pattern and also affect future trip demands. Therefore, in estimating traffic demands, it is very important to consider the industrial park development. This study aims to improve the methodology in estimating a freight trip generation rate with the data based on a nationwide commodity freight survey. The result showed that it is desirable to apply freight trip generation rate by the industry sector in estimating freight trip generations and using the production area of firm as an indicator. Specially, the reliability of the rates through a survey could be made sure because a sample rate based on firms in industrial parks was over 25% and the response rate was over 67%. The sample rate and response rate are very superior as compared to surveys conducted in many other countries. Because industrial parks have significant effects on forecasting transportation demand in pre-feasibility studies of transport and logistics projects, it is expected that the accuracy of freight trip demands would be improved through the results of this study.
박민철(Park Minchoul),김수현(Kim Suhyeon),박창호(Park Changho),전경수(Chon Kyungsoo) 대한토목학회 2007 대한토목학회논문집 D Vol.27 No.3D
도로공사, 교통사고, 기상조건악화 등의 비반복적 돌발상황은 도로용량을 변동시킴으로써 통행시간의 불확실성을 야기한다. 최근 이러한 교통망의 불확실성을 고려하기 위한 교통망 성능지표로서 통행시간 신뢰도가 도입되었으며 교통망의 설계에 이를 반영하고자 하는 노력이 진행되고 있다. 본 연구에서는 도로용량의 확률적 변동을 반영한 기종점 통행시간 신뢰도 제약을 가진 연속적 교통망 설계문제를 구축하고 교통망의 최적개선안을 도출하고자 하였다. 기종점 통행시간 신뢰도는 도로용량집합의 확률적 발생, 통행배정, 기종점 통행시간 수집의 일련의 시뮬레이션 과정을 반복하여 얻어지며 이를 고려한 도로용량의 최적개선해는 시뮬레이션 기반의 유전자 알고리즘을 이용하여 도출되었다. 간단한 예제교통망을 대상으로 실험을 수행한 결과 링크의 용량변동으로 인하여 불확실성이 존재하는 상황에서 기종점 통행시간 신뢰도를 보장하는 정량적인 도로용량 개선해를 찾을 수 있었다. 기종점 통행시간 신뢰도 제약을 포함하지 않은 모형과 비교함으로써 기종점 통행시간 신뢰도의 향상 효과를 확인하였으며 구축된 설계문제에 포함된 기대통행시간 신뢰도수준, 예산수준 등 모수들의 변동에 따른 영향을 파악함으로써 기종점 통행시간 신뢰도를 고려하기 위한 합리적인 설계방안을 마련할 수 있었다. Non-recurrent traffic incident, such as road construction, traffic accident and bad weather condition fluctuates roadway capacity and incurs the uncertainty of travel time. Travel time reliability, as a transportation network performance measure, which may reflect the travel time uncertainty was introduced to network analysis. Recently, researches which applies network reliability concept to transportation network design area were being performing. To reflect fluctuation of link capacity to transportation network design, a continuous network design problem (CNDP) with travel time reliability constraint was formulated as a bi-level model in this study. A simulation-based genetic algorithm with the penalty method was used to obtain the optimal capacity enhancement of each link, combining with a separate module which estimates travel time reliability under link capacity fluctuation. The effect of the travel time reliability constraint on a CNDP was analyzed through a numerical experiment using a simple network. Additionally, the effects of budget allocation and factors to be specified in the model on the results were analyzed.
Bus Signal Priority Strategies for Multi-directional Bus Routes
김수현,전경수,Minchoul Park 대한토목학회 2012 KSCE JOURNAL OF CIVIL ENGINEERING Vol.16 No.5
Though the Bus Signal Priority (BSP) system is well known as an effective way to enhance the service quality of bus travel, the effectiveness of the BSP system significantly depends on the traffic and network conditions. Particularly, most previous use of the BSP system were applied as a corridor-based strategy targeting a few bus lines moving on a corridor; hence existing BSP systems cannot guarantee the service quality of all of the buses in a complex and congested network conflicted by numerous bus lines. Therefore, an appropriate signal priority strategy should be identified before the introduction of a BSP system according to the network conditions. As an alternative to the corridor-based signal priority strategy, this study proposes a Multi-directional Bus Signal Priority (MBSP) approach and analyzes the effectiveness of different priority strategies given various network conditions using the simulation tool Paramics. In addition, to manage conflicting and competing requests, a priority-based rule is proposed and compared with the First-In-First-Service (FIFS) rule. The simulation results showed that a corridor-based BSP was effective for a concentrated bus network, whereas it might deteriorate other traffic flows with little improvement of the bus service for a diverse bus network. For a diverse bus network, other strategies apart from the priority-based MBSP strategy cannot be expected to improve the reliability of bus service. Though the Bus Signal Priority (BSP) system is well known as an effective way to enhance the service quality of bus travel, the effectiveness of the BSP system significantly depends on the traffic and network conditions. Particularly, most previous use of the BSP system were applied as a corridor-based strategy targeting a few bus lines moving on a corridor; hence existing BSP systems cannot guarantee the service quality of all of the buses in a complex and congested network conflicted by numerous bus lines. Therefore, an appropriate signal priority strategy should be identified before the introduction of a BSP system according to the network conditions. As an alternative to the corridor-based signal priority strategy, this study proposes a Multi-directional Bus Signal Priority (MBSP) approach and analyzes the effectiveness of different priority strategies given various network conditions using the simulation tool Paramics. In addition, to manage conflicting and competing requests, a priority-based rule is proposed and compared with the First-In-First-Service (FIFS) rule. The simulation results showed that a corridor-based BSP was effective for a concentrated bus network, whereas it might deteriorate other traffic flows with little improvement of the bus service for a diverse bus network. For a diverse bus network, other strategies apart from the priority-based MBSP strategy cannot be expected to improve the reliability of bus service.