Sangyoup Kim

Roadside walking environments and major factors affecting pedestrian level of service

This paper provides study results of the pedestrian level of service (LOS) within the roadside walking environments. The comfort needs of pedestrians and the multimodal LOS are the main issues of the study. The approach applied in the research includes a literature review, a pedestrian intercept survey, and a multiple regression analysis. Major findings include: (1) current measure of effectiveness for determining pedestrian LOS in the Korean Highway Capacity Manual should be replaced with a more realistic measure of effectiveness, such as the level of pedestrian satisfaction, (2) pedestrian perception within roadside walking environments was successfully captured in a model developed in this study, and (3) the impact of adding automobile-related variables to explanatory variables was statistically significant. Cross-section design elements affecting the perception of pedestrian LOS were also identified. It is hoped that this research will provide an increased understanding for pedestrian-friendly strategies in urban arterial designs.

Freeway Crash Frequency Model Development Based on the Classification of Geometric Alignment Type

This paper presents how one can investigate the effects on crash occurrence of freeway geometric design elements including the horizontal, vertical alignment and road environment. At present, the available research results for the most part involve geometric data analysis that are obtained along a relatively long section of freeway, and, because of the long section`s diverse geometric conditions, the results tend to miss the specific local geometric impacts on vehicle crashes. In this regard, this research attempts to establish vehicle crash models based on a set of freeway geometric patterns whose crash generating characteristics are identical because they are homogeneous in terms of producing the same vehicle operating speeds, and subsequently their actual relationships are described by providing statistical analysis made in this research. Also each standard is comprised of part of straight, curve and continuous curve. This research has revealed that each type of model has different relation between accident and geometry structure. This research results should be useful for doing more reasonable highway designs and safety audit analysis.

A Study of Roundabout Operation According to the Pedestrian Volume

Roundabouts, which belong to traffic circles, are intersections which are similar to the existing rotary form. Roundabouts recently have been constructed all around the world. And interests in roundabouts are increasing in Korea. However, there are lacks of research on pedestrian volume which has a great influence on operation efficiency of roundabouts in urban area. Therefore, this study suggests efficiency analysis and pedestrian signals in roundabouts according to the pedestrian volume. First, VISSIM simulation was organized to analyse volume of one lane roundabouts in urban area. Second, average delay of intersections was calibrated by VISSIM simulation dividing signalized intersections and non-signalized intersections depending on pedestrian volume. Finally, this study showed that roundabouts are suitable when pedestrian volume was under 200person/hr and traffic circles with a pelican signal are suitable when pedestrian volume was over 200person/hr. And when pedestrian volume and traffic volume are over 600person/hr and 1,500vph respectively, fixed signalized intersections fit well.

Pedestrian Conflicts, Pedestrian Comfort Levels, and Current Pedestrian Levels of Service

The current methodology of analyzing pedestrian levels of service stated in the KHCM (Korean Highway Capacity Manual) excludes pedestrian comfort from its primary measures of effectiveness, resulting in mismatching levels of service calculated with the KHCM and the ones stated by pedestrians on the basis of comfort. This can lead to undesirable designs of pedestrian facilities, and in order to deal with this problem a research was carried out to apply the concept of pedestrian conflict for assessing pedestrian comfort. The approach adopted in this study included recalibrating relationships between pedestrian flow and pedestrian conflict and making adjustments to pedestrian levels of service given in the KHCM. In this effort, characteristics of pedestrian flows and conflicts for five field sites located in Seoul were investigated by using video cameras, and selected pedestrians on the five sites were interviewed to determine their levels of comfort for the given walking conditions. Based on these field survey data, this study then demonstrated that there were close relationships between pedestrian comfort, flow rate, density, and pedestrian conflict. A follow-up adjustment to pedestrian levels of service in the KHCM was proposed by this study and an additional survey of pedestrians discovered that the proposed adjustment would better explain how pedestrian comfort levels change with pedestrian flow for a given facility.

Driving Behaviors, the Brainwave Test, and the Distribution of Superelevation and Side Friction Factors for the SMART Highway

This paper demonstrates how the distribution of superelevation and side friction factors over a range of curve radius changes in designing a SMART highway that will be a new design higher-speed 140 km/h highway. The brainwave test and a field study of vehicle speed were carried out in the research to determine proper rates of superelevation and corresponding side friction factors on such high-speed highways. The brainwave test result showed that adjusted side friction factors over a range of curve radius should be applied in SMART highway design. This is due to the driver’s changed behaviors on high-speed designed highways, in particular their cautious speed behaviors and sensitive perception of side friction forces. Traditionally, highway engineers applied the Ball-Bank indicator to capture drivers’ feelings of discomfort on highway curves, but this research demonstrated that the brainwave test would be a better alternative.

Acceleration and Deceleration Profile Development of Reflecting Road Design Consistency

PURPOSES : Previous Speed Profile reflects the patterns of speeds in sections of tangents to curves in the roads. However these patterns are uniform of speeds and Acceleration/Deceleration. In oder to supplement these shortcomings. this study made a new profile which can contain factors of Acceleration/Deceleration through theories of Previous Speed Profiles. METHODS : For sakes, this study developed the speed prediction model of Rural Multi-Lane Highways and calculated Acceleration/Deceleration by appling a Polynomial model based on developed speed prediction model. Polynomial model is based on second by second. Acceleration/Deceleration Profile is developed with the various scenarios of road geometric conditions. RESULTS : The longer an ahead tangent length is, The higher an acceleration rate in curve occurs due to wide sight distance. However when there are big speed gaps between two curves, the longer tangent length alleviate acceleration rate. CONCLUSIONS : Acceleration/Deceleration Profile can overview th patterns of speeds and Accelerations/Decelerations in the various road geometric conditions. Also this result will help road designer have a proper guidance to exam a potential geometric conditions where may occur the acceleration/deceleration states.

A Study on the Effects of Factors of Traffic Accidents Caused by Frozen Urban Road Surfaces in the Winter

PURPOSES: According to accident statistics for road built in 2004, the ratio of accidents on frozen roads to normal roads is 0.9%, whereas the fatality ratio is 2.7%. The risk of accidents on frozen roads is very high. Measures taken every year to prevent traffic accidents of frozen roads in the winter season are still insufficient. Additionally, measures have been established mainly on rural roads. Therefore, for urban roads, analyses and measures to prevent accidents are lacking. In this study, data on accidents on frozen roads was used to search for the causes behind these accidents and measures to reduce accidents have been recommended. METHODS: In this study, collected data from the TAMS (Traffic Accident Management System), which were collected by the Seoul National Police Agency was used. The data were divided into vehicle, people, and condition of road. The analytical model used here was the Logistic Regression Model, which is frequently used for traffic safety and accident analysis. This study uses the odds ratio analysis to search for variables related to frozen road traffic accidents in each category. A total of 18 out of 47 variables were found to be the causes of accidents. RESULTS: From the results of the comparative analysis of 18 variables, the category of the condition of the road was found to be the most critical. Contrary to expectations, more accidents occurred in clear weather than in other conditions. Accidents on bridges occurred frequently, and its odds ratio was the highest compared with other road types. When BPT is operated, the probability of accidents on frozen roads is lower than in general conditions, and accidents occurred frequently on roads with less than four lanes. CONCLUSIONS : Based on the results of this study, suggestions for reducing the risk of future domestic road accidents in freezing conditions are indicated as follows. First, it is necessary to perform a technical review of the urban road traffic accidents caused by frozen roads. Second, it is necessary to establish criteria for the study of the road environment based on the major causes of road accidents on frozen roads. Third, improvements in urban road environmental factors should be made.

Study on Design Principle of Reverse Curve in Superhighway

PURPOSES : This study is to conduct the research on the design principle for the driver`s safety and comfort in installing consecutive curves of superhighway. METHODS : Superhighway does not currently exist in domestic area. Thus, this study is conducted by collecting driving behavior usage of 30 people who are involved in the members of the virtual driving simulation. By identifying the distribution characteristics of each scenario in ANOVA & Tukey Test, the distribution are categorized into three groups. RESULTS : In the case of Group A in Section 3 (R2 entry part), lane departure exceeds the safety standard, which means to be risky condition. And then in the case of Group B and C, the lane departure values applying theoretical formula was evenly distributed compared to the proven values. CONCLUSIONS : Based on the result, the continuous curve design principles at superhighway should follow three standards as follow. First, an additional linear part needs to be inserted between two curves. Second, what if inserting the linear part is difficult, it would be better to insert a curve more than 2,000m. Third, R1/R2 ratio should not be over two. This design primarily aims to the safety of the operator. Such road alignment also meets the expectations of drivers, thus, it may help drivers to be compatible and amenable while driving continuous curve in superhighway.

A Study for Distribution Methods Between Superelevation and Side Friction Factor Reflecting Ergonomic Characteristics by Increasing Design Speed

PURPOSES: The purpose of this study is to develop a method for distribution between superelevation and side friction factor by increasing design speed. METHODS: First of all, a method for distribution between superelevation and side friction factor and a theory for the functional formula of side friction factor in compliance with horizontal radius applied in South Korea and the United States are considered. Especially, design speed of 140km/h and numerical value of design elements are applied to the theory for the functional formula of side friction factor in AASHTO`s methods. Also, the anxiety EEG upon running speed is measured to reflect ergonomic characteristics through field experiments at seven curve sections of the West Coast Freeway, and this data is applied to graph for the functional formula of side friction factor. RESULTS : Matching side friction factor against the anxiety EEG, the results that a critical points of driver`s anxiety EEG sharply increase locate under existing parabola are figured out. CONCLUSIONS : Therefore, we could get a new type of the functional formula that driver`s driving comfortability is guaranteed if the existing the functional formula of side friction factor goes down under boundary of the critical points of the anxiety EEG.

A Study for Influence of Sun Glare Effect on Traffic Safety at Tunnel Hood

PURPOSES : In Korea, over 70 percent of the land consists of mountainous and rolling area. Thus, tunnels continue its upward trend as road network are extended. In these circumstances, the importance of tunnel has been increased nowadays and then its safety investigation and research should be performed. This study is focus on confirming and improving the safety of tunnel. On tunnel hood, sunglare effect can irritate driver`s behavior instantly and this can result in incident. METHODS : The study of this phenomenon is rarely conducted in domestic and foreign papers, so there is no proper measure for this. This study analyzes the driving environment of the effect of sunglare effect on tunnel hood. RESULTS : Traffic accidents stem from complex set of factors. This study build the Traffic Accident Prediction Models to find out the effect of sunglare effect on tunnel`s hood. The independent variables are traffic volume, geometric design of road, length of tunnel and road side environment. Using these variables, this model estimates accident frequency on tunnel hood by Poisson regression model and Negative binomial regression model. Although Poisson regression model have more proper goodness of fit than Negative binomial regression model, Poisson regression model has overdipersion problem. So the Negative binomial regression model is used in this analysis. CONCLUSIONS : Consequently, the model shows that sunglare effect can play a role in driving safety on tunnel hood. As a result, the information of sunglare effect should be noticed ahead of tunnel hood so this can prevent drivers from being in hazard situation.