• Journal of the Korean Society of Safety
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• v.32 no.3
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• pp.123-129
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• 2017

This study deals with the traffic accident of truck at circular intersection. The purpose of this study is to develop the truck accident models based on type of accident and conflict. In pursuing the above, the study gives particular attentions to selecting the appropriate models among Poisson and Negative binomial models using statistical program LIMDEP 8.0. The traffic accident data from 2007 to 2014 are collected from TAAS data set of Road Traffic Authority. Such the dependent variable as number of truck accidents and the 24 independent variables as geometry, traffic volume and others are used. The main results are as follows. First, 5 Poisson models (${\rho}^2$ of 0.164~0.351) which are all statistically significant are selected. Second, the common variable based on type of accident and conflict is analyzed to be truck apron width. The specific variables are, however, evaluated to splitter island, area of splitter island, speed limit sign, truck apron, number approach road, circular intersection sign, speed hump and traffic volume. Finally, widening the truck apron width and improving the above specific variables are analyzed to be important for truck accident reduction at circular intersections.

• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.129-134
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• 2017

This study aims to develop the traffic accident models by circular intersection type using count data model. The number of accident, the number of fatal and injured persons(FSI), and EPDO are calculated from the traffic accident data of TAAS. The circular intersection accident models are developed through Poisson and negative binomial regression analysis. The main results of this study are as follows. First, the null hypotheses that there are differences in the number of traffic accidents, FSI and EPDO by type of circular intersections are rejected. Second, the scale of intersection(median, large), number of approach road, mean width and length of exit road, area of the circulating roadway and central island are selected as factors influencing the number of traffic accidents, FSI and EPDO in rotary. Third, the scale of intersection(median), guide signs(limited speed, direction, roundabout), number of approach road, entry angle, area of the intersection and central island are adopted as factors influencing the number of traffic accidents, FSI and EPDO in roundabout. Finally, transferring from rotary to roundabout could be expected to make the accident decrease.

• Journal of the Korean Society of Safety
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• v.30 no.2
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• pp.70-76
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• 2015

This study deals with the traffic accident of circular intersections. The purpose of the study is to develop the accident models by traffic violation type. In pursuing the above, this study gives particular attention to analyzing various factors that influence traffic accident and developing such the optimal models as Poisson and Negative binomial regression models. The main results are the followings. First, 4 negative binomial models which were statistically significant were developed. This was because the over-dispersion coefficients had a value greater than 1.96. Second, the common variables in these models were not adopted. The specific variables by model were analyzed to be traffic volume, conflicting ratio, number of circulatory lane, width of circulatory lane, number of traffic island by access road, number of reduction facility, feature of central island and crosswalk.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.2D
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• pp.209-215
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• 2011

Roundabout has circular traffic island in the intersection center and is kind of intersection where the automobile bypass circular traffic island. In Korea, the provisional Roundabouts Design Guidelines were published in 2004 by MLTM (Ministry of Land, Transport and Maritime Affairs). This guideline did not discussed domestic traffic circumstance. It just only introduced foreign instances and their guidelines. In addition, the recent National Competitiveness roundabouts as part of the green growth has been concentrated on the interest. In this paper, 90 degree of the 4-legged roundabout was compared with 72 degree, 45 degree, and 30 degree 5-legged roundabouts by micro simulation VISSIM. As a result of analysis, average travel time is decreased when the inscribed circle diameter become bigger the roundabout. 5-legged roundabout until 2,000 volume per hour evaluated to be similar effect at 90 degree of 4-legged roundabout.

• Journal of the Korean Society of Safety
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• v.32 no.4
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• pp.107-113
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• 2017

This paper deals with the traffic factors related to the collisions of circular intersections. The purpose of this study is to develop traffic accident models by type of collision based on land use. In pursuing the above, the traffic accident data from 2010 to 2014 were collected from the "Traffic Accident Analysis System (TAAS)" data set of the Road Traffic Authority. A multiple regression model was utilized in this study to develop the traffic accident models by type of collision. 17 explanatory variables such as geometry and traffic volume factors were used. The main results are as follows. First, the null hypothesis that the type of land use does not affect the number of accidents by type of collision is rejected. Second, 10 accident models by type of collision based on land use are developed, which are all statistically significant. Finally, the ADT, inscribed circle diameter, bicycle lane, area of central island, number of speed hump, circulatory roadway width, splitter island, area of circulatory roadway, mean number of entry lane and mean width of entry lane are analyzed to see how they affect accident by type of accident based on land use.

• International Journal of Highway Engineering
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• v.20 no.2
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• pp.75-85
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• 2018

PURPOSES : This study aimed to analyze traffic accidents at circular intersections, and discuss accident reduction strategies based on land use and vehicle type. METHODS : Traffic accident data from 2010 to 2014 were collected from the "traffic accident analysis system" (TAAS) data set of the Road Traffic Authority. To develop the accident rate model, a multiple linear regression model was used. Explanatory variables such as geometry and traffic volume were used to develop the models. RESULTS : The main results of the study are as follows. First, it was found that the null hypotheses that land use and vehicle type do not affect the accident rate should be rejected. Second, 16 accident rate models, which are statistically significant (with high $R^2$ values), were developed. Finally, the area of the central island, number of speed humps, entry lane width, circulatory roadway width, bus stops, and pedestrian crossings were analyzed to determine their effect on accidents according to the type of land use and vehicle. CONCLUSIONS : Through the developed accident rate models, it was revealed that the accident factors at circular intersections changed depending on land use and vehicle type. Thus, selecting the appropriate location of bus stops for trucks, widening entry lanes for cars, and installing splitter islands and optimal lighting for motorcycles were determined to be important for reducing the accident rate. Additionally, the evaluation showed that commercial and mixed land use had a weaker effect on accidents than residential land use.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.6
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• pp.133-143
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• 2018

Roundabouts are generally installed at which traffic and pedestrian volume is relatively small intersections, and hence traffic can flow one direction around a circular island without traffic lights. A number of researches for roundabout signal metering have been processing ways to deal with operation efficiency drops in conditions of unusual traffic and pedestrian volume increases. However, there is still a shortcoming exists in previous operation algorithm does not consider the hidden vehicles between yield lines and detectors and queueing vehicles in circular lanes. These queueing vehicles between them can be cleared by introducing the queue clearance time. The purpose of this research is developing a real time signal metering operation algorithm by considering the vehicle queue clearance time. The results of varying queue clearance time application show that there is a substantial average vehicle delay reduction in VISSIM Com-Interface simulation. When the total number of entering vehicle is 3,200~4,800 vehicle/hour with varying queue clearance time application 21~50 seconds gives average delay reduction per vehicle by 16.1~71.7%.

• Journal of Korean Society of Transportation
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• v.35 no.4
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• pp.321-331
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• 2017

The objective of this study is to analyze the factors affecting the pedestrian accidents of roundabout near schools. To this end, this study has focus on the comparative analysis of pedestrian accidents across different school areas. The traffic accident data from 2007 to 2014 are collected from TAAS data set of Road Traffic Authority. To develop the pedestrian accident rate model, the linear regression model has been utilized in this study. 28 explanatory variables such as geometry and traffic volume factors are used. The main results are summarized as follows. First, the null hypotheses that the number of pedestrian accidents are the same are rejected. Second, 5 multiple linear regression accident models with higher statistical significance (adjusted $R^2$ of 0.651~0.788) have been developed. Third, while the common variables of 3 models (model I~III) related to school location are evaluated to be the pedestrian island, crosswalk, types of roundabout, elementary school and bus stop. Fourth, while the common variable of 3 models (model III~V) related to near school area or not is evaluated to be pedestrian island, type of roundabout, sidewalk, elementary school, speed hump, speed limit sign and number of entry lane. As a result, the installation of pedestrian islands and crosswalk might be expected to decrease the number of pedestrian accidents near schools.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6D
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• pp.623-636
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• 2012

Roundabout is an intersection that allows vehicles to pass through the intersection by circulating the circular traffic island at the center of the intersection. In this study, a comparative analysis was conducted on roundabout at five locations in order to deduce the operational result and financial effect of roundabout and signal intersection. As for the operational result, it was found that roundabout showed improvement effect in the average delay per vehicle compared to that of signal intersection by minimum of 65.6% and maximum of 91.77%. it was found that roundabout showed financial cost-saving effect in the traffic congestion cost compared to that of signal operation by minimum of 58.59% and maximum of 81.69% per year. It can be known from these analysis results that roundabout has significant operational effects under certain amount of traffic volume by allowing vehicles to pass through the intersection in a continuous way without much waiting time and stoppage from signal control.

• Journal of Korean Society of Transportation
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• v.31 no.6
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• pp.43-52
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• 2013

A roundabout is a form of circular intersection in which traffic travels counterclockwise around a central island and in which entering traffic must yield to circulating traffic. It has been known that a roundabout provides substantially better operational and safety characteristics than other intersections including rotaries. Recently, a roundabout has started to be constructed due to its efficiency, safety, and other advantages of a roundabout comparing other intersections in Korea. However, there has been no guideline to be used to decide appropriate intersection types considering given conditions of the intersections. To solve this problem, the guideline with traffic volume to choose the suitable intersection types was developed based on analysis results using the SIDRA software which is generally used to analyze operational effects of roundabouts. It was found that a roundabout is more efficient than signalized intersection when the traffic volume is between 125 and 450 veh/h on one lane road and roundabout is not recommended when there are more than 30% left turn traffic. The optimal traffic volume provided in this research will be usefully used in planing and designing roundabouts in Korea.