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Development of Free Flow Speed Estimation Model by Artificial Neural Networks for Freeway Basic Sections  

Kang, Jin-Gu (한국토지공사 신도시사업1처)
Chang, Myung-Soon (한양대학교 교통시스템공학과)
Kim, Jin-Tae (교통개발연구원)
Kim, Eung-Cheol (인천대학교 토목환경시스템공학과)
Publication Information
Journal of Korean Society of Transportation / v.22, no.3, 2004 , pp. 109-125 More about this Journal
Abstract
In recent decades, microscopic simulation models have become powerful tools to analyze traffic flow on highways and to assist the investigation of level of service. The existing microscopic simulation models simulate an individual vehicle's speed based on a constant free-flow speed dominantly specified by users and driver's behavior models reflecting vehicle interactions, such as car following and lane changing. They set a single free-flow speed for a single vehicle on a given link and neglect to consider the effects of highway design elements to it in their internal simulation. Due to this, the existing models are limitted to provide with identical simulation results on both curved and tangent sections of highways. This paper presents a model developed to estimate the change of free-flow speeds based on highway design elements. Nine neural network models were trained based on the field data collected from seven different freeway curve sections and three different locations at each section to capture the percent changes of free-flow speeds: 100 m upstream of the point of curve (PC) and the middle of the curve. The model employing seven highway design elements as its input variables was selected as the best : radius of curve, length of curve, superelevation, the number of lanes, grade variations, and the approaching free-flow speed on 100 m upstream of PC. Tests showed that the free-flow speeds estimated by the proposed model were statistically identical to the ones from the field at 95% confidence level at each three different locations described above. The root mean square errors at the starting and the middle of curve section were 6.68 and 10.06, and the R-squares at these points were 0.77 and 0.65, respectively. It was concluded from the study that the proposed model would be one of the potential tools introducing the effects of highway design elements to free-flow speeds in simulation.
Keywords
고속도로;설계요소;속도추정모형;인공신경망;자유속도;
Citations & Related Records
Times Cited By KSCI : 2  (Citation Analysis)
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