PURPOSES : This study sought ways to connect urban above ground roads and underground roads to utilize urban space more efficiently in the development of underground roads, which are currently under development in order to alleviate problems caused by oversaturated above-ground roads. A simulation analysis was performed to develop an operation strategy that connects above-ground and underground roads to prevent congestion in above-ground areas such as entrances and exits from transferring to underground roads as well as to present its effectiveness. METHODS : Traffic efficiency analysis according to the operation strategy of above ground and underground roads was conducted using VISSIM, a microscopic traffic simulation software. The functions implemented in VISSIM were collected to set effectiveness analysis indicators for each underground road operation strategy. The Shinwol-Yeoui Underground Road was selected as the spatial scope of this study, and a surrounding road network was constructed. In addition, full-scale simulation analysis preparations were completed by performing network calibration based on the actual traffic attribute data of underground and surrounding surface roads within the construction scope. Accordingly, a traffic efficiency evaluation analysis was conducted based on the underground road operation strategy. CONCLUSIONS : Information on the increase in traffic volume within the Shinwol-Yeoui underpass was collected every 15 min. The analysis was divided into an analysis of the traffic situation within the underpass through demand control when the service level reached level D and an analysis of when demand control was not performed. It was found that demand control was necessary for the Shinwol-Yeoui Underpass when the internal traffic volume reached 2,500 vehicles/h. In addition, to analyze the spread of traffic and congestion owing to the weaving phenomenon caused by lane changes in the underpass, an analysis was conducted to observe the traffic improvement effect when full lane changes are possible for the Shinwol-Yeoui Underground Road, which currently has some lane-change-permitted sections. The analysis showed that both the maximum traffic volume and average travel speed showed better results when lane changes were allowed, and the communication situation at Yeoui JCT was found optimal.

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 : The primary purpose of this study is to develop a framework for predicting the demand and distribution of pedestrians when an open space zone is built at the top through the undergroundization of the Gyeongin Expressway. METHODS : After analyzing the current status through a survey on the number of people, students, surrounding traffic volume, and future socioeconomic indicators, the rate of change in the floating population and the rate of increase and decrease in the traffic volume of pedestrians were calculated to evaluate the effect. In addition, microscopic analysis results were derived by setting a pedestrian analysis zone (PAZ). A walking environment index (WEI) was developed that can quantitatively evaluate the degree of walking activation by indicating walking-related surrounding environmental factors. Based on this, a walking demand prediction model was developed. In addition, the results were validated by calculating the walking volume through a micro-simulation in/around the open space zone. RESULTS : The number of crosswalks and schools, transit development indicators, and pedestrian volume increased as the WEI value increased. However, the log form of the distance was observed to be a factor that reduced walking. CONCLUSIONS : This study attempted to reliably predict the demand for walking on the Gyeongin Expressway by calculating the amount of induced walking and the amount of passing walking. The pedestrian demand can be boosted by improving walking environments.

PURPOSES : It is necessary to implement traffic-control strategies for underground roads. In this study, the application criteria for traffic control were developed to minimize actual traffic congestion on underground roads before it occurs. In particular, the traffic congestion judgement criteria and procedure (TJCAP) were developed. They can specifically classify the possibility of traffic congestion underground. METHODS : A microscopic traffic simulation model was used to analyze different scenarios. With the scenario simulation results, a hierarchical clustering analysis was applied to produce quantitative values from the TJCAP for each experimental network case. RESULTS : For network case (a), it was concluded that the possibility of traffic congestion on underground roads increases when the speed of the ground road connected to the main underground road and the connected ground road after the outflow of the ramp section is low. When the connected road is an interrupted facility after entering the underground roads, the red time is long, and when the section travel speed is 15 km/h, the possibility of traffic congestion underground is highest. A cluster analysis based on these results was performed using two techniques (elbow and silhouette) to verify the final classification. CONCLUSIONS : The TJCAP were designed to operate traffic flow with stricter criteria than traffic congestion management on ground roads. This reflects the difference in the driving environment between underground and above-ground roadways.