Jaisung Choi

A Multinomial Logit Model of Pedestrian–Vehicle Crash Severity

ABSTRACT This article estimated a multinomial logit model to identify the factors determining the severity of pedestrian–vehicle crashes in South Korea. Our results showed that relative to minor crashes, fatal and serious crashes were associated with collisions involving heavy vehicles; drivers who were drunk, male or under the age of 65; pedestrians who were over the age of 65 or female; and pedestrians who were hit in the middle of the road, on high speed roads, in inclement weather conditions, at night, on road links, in tunnels, on bridges, or on wider roads.

Factors associated with crashes involving taxi owners and non-owners: A case of moral hazard and adverse selection?

Taxis experience a higher risk of a motor vehicle crash partly because of their much higher levels of exposure on the roads. Although several studies have been conducted to examine the factors associated with the frequency and severity of taxi collisions, little research has been conducted to examine the differences in the factors associated with owner taxis and non-owner taxis. This study finds that collisions involving non-owners are more likely to be associated with poor or risky driving behaviors than collisions involving taxi vehicle owners. This result is consistent with the economic principles of moral hazard and adverse selection. Hence, policy makers responsible for traffic safety, taxi regulation or taxi operations should consider measures to reduce these market inefficiencies and improve the safety of not only taxi drivers but all road users.

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.

Application Methodology of Greenhouse Gases Emission Table for Various Types of Roads and Vehicles

PURPOSES : This study aimed to offer a greenhouse gases table to assist a road designer in calculating the greenhouse gases for a road environment when making a decision about an alternative road. METHODS : This study developed an operation mode table of greenhouse gases using the MOVES program. Similar factors for Korean vehicles and fuels are reflected in the MOVES program, which was made in the USA. Finally, a paired t-test was conducted to calculate the site data and MOVES data. Through these studies, a methodology was suggested for calculating carbon emissions based on various types of roads alignments. RESULTS : The site results for a passenger truck on the road were statistically significant when the vehicle speed was above 65 km/h. However, a future study will consider factors for various road alignments and vehicles. CONCLUSIONS : This study will contribute to the theoretical basis for reducing carbon emissions from roads by helping road designers make decisions about road alternatives in terms of the road environment.

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.

Estimation of Greenhouse Gas Emissions as Highway Design Types by Using Driving Simulator

PURPOSES : This study devotes its energies to estimate greenhouse gas emissions for types of horizontal highway designs. METHODS : This paper suggested two types of road scenarios, scenario 1 is made by the lack of road design consistency. Beside scenario 1, scenario 2 is made by good road design. For comparisons of greenhouse gas emissions, driving simulator was used. RESULTS : Emission rates of road scenario 1 are 1.4 times higher than scenario 2 in the driving simulator. CONCLUSIONS : This study may have important implications for contributing to the application of road alignment technology for reduction of greenhouse gases as quantifying the correlations between greenhouse emissions and various road alignments. Consequently, this study will help road designers determine which roads are best alternatives in the process of choosing the roads in the future in terms of environmental benefits.

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 method for the estimation of greenhouse gas emissions based on road geometric design and its application to South Korea

ABSTRACT South Korea has the tenth highest greenhouse gas (GHG) emissions worldwide, of which 16% originates from the road sector. Existing estimation methods of road GHG emissions have various limitations, such as low accuracy or the ability to only estimate GHG emissions within a limited area. Therefore, this study aimed to develop a methodology to estimate GHG emissions while considering various geometric designs of roads, including both vertical and horizontal alignment. The developed method is more objective and reliable than existing methodologies that consider only vertical alignment. First, Lamms theory on travel speed profiles was applied to predict GHG emissions. Then, this study attempted to overcome the limited spatial estimation capacity of existing methods by considering upstream and downstream geometric design parameters simultaneously. Second, this study used the GHG operation mode extracted from the MOtor Vehicle Emission Simulator (MOVES), a modeling system that estimates emissions for mobile sources at the national, county, and project levels for criteria air pollutants, GHGs, and air toxicity. The operation mode includes vehicle type, fuel, and other factors, and is designed to estimate GHG emissions at 1-s intervals. Based on the results of the analysis, the effectiveness of the new method was compared to existing methods using an economic analysis (e.g., cost–benefits from the reduced emissions). This study presents a method for performing sensitive estimations of GHG emissions according to the geometric design of roads, which can be used to collect more accurate data on GHG emissions.