PURPOSES : This study is to evaluate environmental improvement effects of underground road project, as a case study of ‘Seobu’underground expressway project in Korea. METHODS : The environmental improvement effects of underground road construction were classified into tree sector in this study – air quality, noise, and thermal environment. To evaluate these effects, this study collected and divided environment dataset into before, during, and after ‘Seobu’underground expressway construction, and compared the change of values with entire city. In addition, the quantification method of environmental improvement effects was suggested based on the literature review. RESULTS : The result of this study indicates that there exist significant improvement effects of urban environment after the construction of ‘Seobu’underground expressway. Specifically, the concentration of particulate matters (PM10) and daytime/nighttime noise, and land surface temperature (LST) were improved along the expressway. In addition, the overall environmental benefit of ‘Seobu’ underground expressway was estimated to 1.15 billion won per year. CONCLUSIONS : To promote systematic and consistent underground road project, it is required to establish legislative system for evalauting and supporting urban improvement effects.

PURPOSES : This study aims to identify the thresholds at which various factors affecting traffic crashes lead to actual traffic crashes METHODS : To verify the thresholds, we created scenarios and ran simulations with a combination of factors that affect traffic crashes. Lateral offset and minimum TTC were used to evaluate whether an incident occurred. RESULTS : In the first scenario, the most significant factor affecting traffic crashes is curvature, and it was found that the smaller the curvature(200 meters or less), the greater the deviation from the lane. And in the second scenario, especially the passenger car scenario, no accidents occurred when the curvature was greater than 90 meters and the speed was 40 km/h or less. The smaller the curvature and the higher the speed, the more accidents occurred. Similarly, in the bus scenario, no accidents occurred when the curvature was 120 meters or more and the speed was 30 km/h or less. Also, accidents tended to occur when the curvature was smaller and the speed was higher. CONCLUSIONS : Through this study, we derived the thresholds of factors that influence traffic crashes. The results are expected to help design and operate roads in the future and contribute to reducing traffic crashes.

of actual and suspicious black-ice cases that occurred during the last 10 years in the Republic of Korea. METHODS : Based on literature review, meteorological observation data associated with black-ice formation are selected: wind speed, air temperature (T), dew point temperature (Td), and relative humidity, to set minimum or maximum threshold values based on the normal distribution of each variable. In addition, weights are assigned based on the relationship among the variables to calculate the probability of occurrence. RESULTS : The threshold values are calculated using the average and standard deviation, resulting in 7.65 °C, 56.63%, 2.99 ms-1 for T-Td, relative humidity, and wind speed, respectively. Whereas the threshold value of T-Td and wind speed is set to the maximum threshold, that of the relative humidity is set to the minimum threshold value. These threshold values are applied to the diagnosis algorithm of black-ice formation, including a 1-h accumulated precipitation. CONCLUSIONS : The algorithm is expected to be utilized as a research methodology for diagnosing suspected cases of black ice.

PURPOSES : This study is performed first to define the aging of road facilities and to analyze the effects of environmental factors on the deterioration of median barriers. METHODS : The aging of road facilities is defined using an analytical hierarchy process (AHP). The first stage is associated with the period, facilities, and maintenance, whereas the second stage is associated with the details. The effects of environmental factors on the deterioration are analyzed by measuring the carbonation depth and compression strength. Two regions, i.e., Gangwon and Busan, are compared separately. Top, middle, and bottom samples are analyzed for both regions. RESULTS : Based on the result of the AHP analysis, weights for period (0.220), function (0.410), and maintenance (0.370) are derived. The average carbonation depths are 11.12 and 9.78 mm for Kangwon and Busan, respectively. The estimated values of compressive strength at Gangwon are 19.7 MPa (Wonju), 24.7 MPa (Samcheok A), and 25.9 MPa (Samcheok B), 20.2 MPa (Haeundae), 23.8 MPa (Yeongdo), and 29.5 MPa (Nam). CONCLUSIONS : The aging of road facilities is associated with subpar functionality and durability. Furthermore, the median barriers constructed in the Gangwon region deteriorated more significantly than those in the Busan region owing to environmental factors. In addition, the bottom samples are more affected by aging than the top samples.

PURPOSES : The objective of this study is to analyze the uniform diffusion mechanism of precursor gas species, and the effect of NOx reduction technology in a full-scale particulate matter testing facility, using computational fluid dynamics (CFD). METHODS : A full-scale environment chamber was constructed to evaluate the effects of particulate matter reduction technologies on the road. CFD analysis was conducted to simulate the road environment conditions in the chamber, and investigate the effect of the NOx removal panel. The time required to reach the NOx concentration to target value in the fluid field was determined at a given inflow velocity, inlet direction, and initial inflow concentration. The effect of the NOx removal panel, and solar energy on the reduction characteristics of the NOx concentration in the environment chamber was analyzed. RESULTS : The inflow velocity was determined to be the major factor affecting the time required to reach a uniform target NOx concentration in the environment chamber. The inlet location in the transverse direction requires additional time to approach the uniform target concentration, than the longitudinal direction at the same inflow velocity. Based on the CFD analysis in the 1ppm concentration condition of the chamber, a two-fold increase in the NOx removal panel efficiency can reduce the time to target concentration by approximately 50%. It is also observed that a 20% increase in solar energy can decrease the time to target concentration by 4%–12% depending on the panel efficiency. CONCLUSIONS : This study proved that a full-scale environment chamber can be effectively utilized to evaluate the particulate matter reduction technologies applied in road facilities

PURPOSES : A pilot experimental study on the formation of fine particulate matter through photochemical reactions using precursor gas species (volatile organic compounds (VOCs), NH3, SO2, and NOx) was conducted to evaluate the large-scale environment chamber for investigating the pathway of aerosol formation and the subsequent assessment techniques used for reducing fine particulate matter. Two small-scale environment chambers (one experimental group and one control group), each with a width, depth, and height of 3 m, 2 m, and 2.3 m, respectively, were constructed using ethylene tetrafluoroethylene (ETFE) films. METHODS : The initial conditions of the fine particles and precursor gases (NOx and VOCs) for the small-scale environment chamber were set up by injecting diesel vehicle exhaust. NH3 and H2O2 were added to the small-scale environment chamber for the photochemical reaction to form organic and inorganic aerosols. The gas phase of the VOCs and the chemical compositions of aerosols were investigated using a proton transfer reaction time-of-flight mass spectrometer and the aerodyne high-resolution time-of-flight aerosol mass spectrometer at 1 and 10 s time resolutions, respectively. Gas phases of NO and NO2 were measured using Serinus 40 NOx at a 20 s time resolution. RESULTS : The small-scale environment chambers built using ETFE films were proved to supply sufficient natural sunlight for the photochemical reaction in the environment chambers at an average of approximately 89% natural sunlight transmission at 300–1000 nm. When the intermediates of NH3 and H2O2 for the atmospheric chemical reaction were injected for the initial condition of the small-scale environment chamber, nitrate and ammonium in the experimental group increased to 4747% and 1837%, respectively, compared to the initial concentrations (5.4 μg/m3 of nitrate and 5.2 μg/m3 of ammonium), indicating the formation of secondary inorganic aerosols of ammonium nitrate (NH4NO3). This implies that it is necessary to inject intermediates (NH3 and H2O2) for the formation of fine particulate matter when simulating the atmospheric photochemical reaction for assessing the environment chamber. CONCLUSIONS : This study has shown that small-scale environment chambers can simulate the atmospheric photochemical reaction for the reduction of fine particulate matter and the formation of the aerosol pathway. The results of this study can be applied to prevent time and economic losses that may be incurred in a full-scale environment chamber.

PURPOSES : In this paper, pedestrian-oriented time assured traffic operation (POTATO), adopted in Korea at a single crossing pedestrianoriented operating area, is explored and applied to a simulation experiment and test site to verify the operation efficiency. METHODS : Three candidate plans are presented as a method to operate pedestrian-oriented signal operations that can overcome the restrictions on signal controllers in Korea. The selected POTATO and TOD signal operations were compared and analyzed. The delay and pedestrian queues, present length, and number of times were used as comparative indices. RESULTS : Scenario-specific simulations confirmed that the delay, compared to TOD signal operation, was reduced by up to 5 s/ped depending on the vehicle traffic volume and the number of pedestrians. For the vehicle delay, the results increased up to 8.99 s/veh, depending on the traffic volume of the vehicles and pedestrians. As a result of the test site operation, POTATO operation improved by 5.12 s/ped (approximately 46.69% improvement) compared to TOD operation in the hours commuting to school and by 2.84 s/ped in the hours commuting from school (approximately 51.13% improvement). In case of vehicle delay, the delay increased by 2.35 s/veh (approximately 64.39%) in the hours commuting to school and 1.20 s/veh (approximately 21.11%) in the hours commuting from school compared to the TOD operation. CONCLUSIONS : Through simulations and test site pilot operation verifications, the effects of pedestrian delay improvement were more positive if POTATO proposed in this study was low in vehicle traffic.