• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.379-390
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• 1994

The recent study of the delay models have assumed random arrival which has a constant average flow rate throughout the cycle. However, where signals are spaced closely together or form part of progressive system, platoon flows are common and more closely represent reality. In such cases, those results are quite different pattern of estimated delay from that of observed one. In order to solve this problem, the 1985 HCM takes Progression Adjustment Factor (PAF) into account. In the 1985 HCM, however, it has deficiencies in defining and applying it, such as platoon ratio ($R_p$) and platoon arrival type. The Purpose of this study is to investigate theoretically the predictive ability of the individual models concerned through comparing the estimated delay and PAF suggested by NCHRP Report 339, KHCM or USHCM (1985) with the observed obtained by field survey at a signalized intersection.

• Journal of Korean Society of Transportation
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• v.32 no.3
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• pp.198-206
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• 2014

According to the statistics of the National Police Agency, red light running (RLR) crashes represent a significant safety issue throughout Korea. This study deals with the RLR crashes occurred at signalized intersections in Cheongju. The objectives of this study are to comparatively analyze the characteristics of between RLR crashes and the Non-RLR crashes, and to find out factors using a Binary Logistic Regression(BLR) model. In pursuing the above, the study gives particular attentions to testing the differences between the above two groups with the data of 2,246 RLR/ 3,884 Non-RLR crashes (2007-2011). The main results are as follows. First, many RLR crashes were occurred in the nighttime and in going straight. Second, the difference between RLR and Non-RLR crashes were clearly defined by crash type, maneuver of vehicle before crash, age of driver (30s, 50s), alcohol use and accident pattern. Finally, a statistically significant model (Hosmer and Lemeshow test : 7.052, p-value : 0.531) was developed through the BLR model.

• Journal of Korean Society of Transportation
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• v.27 no.1
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• pp.157-167
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• 2009

This study deals with the turn penalty functions in the urban transportation demand forecasting. The objectives are to develop the penalty functions of left-turn traffic in the case of signalized intersections, and to analyze the applicability of the functions to the traffic assignment models. This is based on the background that the existing models can not effectively account for the delays of left-turn traffic which is bigger than that of through traffic. In pursuing the above, this study gives particular attention to developing the penalty functions based on the degrees of saturation by simulation results of Transyt-7F, and analyzing the applicability of the functions by the case study of Cheongju. The major findings are the followings. First, two penalty functions developed according to the degrees of saturation, are evaluated to be all statistically significant. Second, the results that the above functions apply to the Cheongju network, are analyzed to be converging, though the iteration numbers increase. Third, the link volumes forecasted by turn penalty functions are evaluated to be better fitted to the observed data than those by the existing models. Finally, the differences of traffic volumes assigned by two functions, which are exponential and divided forms, are analyzed to be very small.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.6
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• pp.24-31
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• 2011

This study deals with the operational effectiveness of roundabout. The roundabout is currently under consideration in our country depending on the result of existing researches, that the roundabout decreases delay and is environmentally friendly compared to the signalized intersection. The purpose of the study is to analyze the operational effectiveness of the roundabout by the change of pedestrian traffic volume. In pursing the above, this study gave particular emphasis to designing a network of roundabout, developing some scenarios for analysis including both entering traffic volume and pedestrians volume, and comparatively analyzing the average controlled delay time per vehicle. In this study, VISSIM model was used as a tool for traffic simulation. The main results are as follows. First, as a result of analyzing a traffic delay based on the pedestrian traffic volume, pedestrian traffic volume was analyzed to have a great impact on the roundabout operation. Second, the more pedestrian traffic volume were evaluated to indicate the more traffic delay. When the entering volumes with 1,000persons/hour (pedestrian volume) were more than 800pcph in the single-lane and 1,600pcph in the double-lane roundabout, the operational efficiencies of signalized intersections were evaluated to be better than those of roundabouts.

• Journal of Korean Society of Transportation
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• v.34 no.1
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• pp.29-42
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• 2016

Speeding is an important factor in traffic safety. Speed not only affects crash severity, but is also related to the possibility of crash occurrence. This study presents results from an analysis of 27,968 speed violation cases collected from 36 red light and speed enforcement cameras at signalized intersections in the city of Cheongju. Data included details of their violation history such as speeding tickets within a recent 3-year span and their demographic characteristics. The goal of this analysis is to understand the correlation between speed violations and various factors in terms of humans, vehicles and road environments. This study used descriptive statistics and Binary Logistics Regression(BLR) analysis with SPSS 20.0 software. The major results of this study are as follows. First, speed violations occurred at rural and suburban area. Second, about 25.6% of the violators committed to more than 20km/h over a speed limit. Third, the difference between speed violators and normal drivers clearly appeared in location of intersection(urban/rural/suburban area), gender and age. Finally, a statistically significant model(Hosmer and Lemeshow test: 11.586, p-value: 0.171) was developed through the BLR.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.1 no.1
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• pp.58-69
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• 2002

Most of the traffic accidents are a rear-end collision and a clash generated in the signalized intersection on the local roads. So, it is demanded that the high-quality of signal control and dilemma zone control. According to the cases generated by foreign countries, we established the strategies which are composed of Volume-Density Control, strategy of the dilemma zone control using R-detector (microwave detector) In Japan and EC-DC Control. MOEs(Measure of effectiveness) are car numbers in the dilemma zone , max-out probability in the safe side and the average stopping delay in the progress side. We choose a signalized intersection in rural highway to analyze the effect of the strategies and practiced an on-the-spot survey. The result of the survey is applied to the basic data in the simulator. Consequently, strategy of the dilemma zone control using R-detector(microwave detector) in Japan is the best effective in the safe side and EC-DC control is the best in the progress side. Based on the result, we developed the effective strategy of the signal control . This strategy is composed of the strategy of Japan and the detector on the stopping line used in the EC-DC control. On the result of the analysis, new strategy is the best effective in two sides.

• International Journal of Highway Engineering
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• v.9 no.4
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• pp.83-92
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• 2007

In 2004, the number of traffic crashes and deaths in Korea are 220,755 and 6,563, respectively. Korea Road Traffic Safety Authority reported that the number of traffic accidents occupies over 25% out of total accidents, and found that traffic crash probability is extremely high at intersections since intersections have various traffic conflict points. A Safety study using Traffic Conflict Technique is much more useful than a study using reported traffic accident data. Existing traffic conflict research hardly considered conflict severity occurring at intersections. So, the study developed new criteria considering conflict severity. Analytic methods precisely detecting crashing points using field surveying data, and applied an application of our new criteria. Opposing left-turn conflict criteria was devided by three groups(high severe conflict, middle severe conflict, and less severe conflict) based on conflict boundary by means of a standard vehicle length. After analyzing field surveying data(3hours), we found totally 41 opposing left-turn conflicts. 3 cases are high severe conflict, and another 10 cases are middle severe conflicts, and the other cases are less severe. Studies related in conflict severity are considerably important to evaluate intersection's detailed safety index, and existing studies(purely conflict counting does not consider severity) have a limitation to clearly determine the level of safety of intersections for an application.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4D
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• pp.527-538
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• 2011

Currently, the only established criteria is on the location of bus stops on principal roads where uninterrupted flow mainly occurs. There are no clear guidelines on any method to locating bus stops considering the characteristics of bus operation and pedestrians. If the location or exterior of a bus stop is inappropriate, road users including bus drivers and pedestrians will be caused serious dangerous and inconvenience. In this study, the research below was performed in order to propose rational criteria for the location of bus stops integrated with or separated from speed-change lanes at signalized intersections considering smooth traffic flow and the characteristics of bus operation and pedestrians as well as traffic safety : First, the appropriate length of each of the near-side and far-side bus stops was calculated by categorizing bus stops to be constructed into those integrated with speed-change lanes and those separated from speed-change lanes. Secondly, the appropriate length of each of the bus stops divided into near-side bus stops and far-side bus stops and integrated with or separated from speed-change lanes was selected by considering the characteristics of pedestrians. Thirdly, whether the construction locations of bus stops were appropriate or not was determined based on the appropriate length of bus stops integrated with or separated from speed-change lanes, which was calculated and selected by considering traffic flow and the characteristics of pedestrians and considering traffic safety. The method for locating bus stops considering traffic flow, the characteristics of pedestrians, and traffic safety will be able to help suggestion criteria of bus stop and the location of safe and pleasant bus stops.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.2
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• pp.63-75
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• 2013

Roundabouts have been operated in Europe, America and Australia since the 1970s, and many relevant researches continually was carried out. Though many studies regarding roundabout have been recently conducted in korea, most of them have focused on its operational safety and efficiency. Moreover, roundabout design guideline did not define a clear criteria related to pedestrian in roundabout, but seldom investigate the influences of pedestrian on crosswalk. In this study, we seek ways to operate the pedestrian crosswalk signal on roundabout maximizing their operational effects in exceptional case such as rush hour or intersection near the special facilities. We proved that roundabout signal operation is effective under certain circumstances in according to the number of pedestrian, and suggested the optimal signal timing plan for signalized roundabouts. For pursuing the above, we conducted the simulation test using the VISSIM model. The results show that the operational effectiveness of signalized roundabout was evaluated to be better than non-signalized roundabout in specific pedestrian volume condition. In addition, those results are confirmed using simulation analysis conducted on the real roundabout.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.269-281
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• 2018

Unlike its archetype predecessor such as the Highway Capacity Manual of the United States, the Korean Highway Capacity Manual of 2013 provides the analytical models for estimating the saturation flow rates for the lane-occupying work-zones in the proximity of the signalized intersections. Direct application of the revised saturation flow rates into the classic control delay models, however, appears to produce unreasonable delay amount as traffic demand approaches lane-group capacities and surpasses them, which is common phenomena in the work-zones. Complex interaction among vehicles, lane-dropping work-zone geometry and signal operations were never accounted in the traditional control delay models, and considerable differences between the delay model outcomes and field observations are repeatedly experienced. This paper proposes the modified approaches to the delay models in the manual, exerted on all three elements of control delay, and particularly focuses on the temporal and spatial boundary expansion in comparing the simulated results to the estimated ones. Extensive microscopic simulation work and calibration effort supports the modified approaches well enough to use them in the work-zone planning and evaluation.