지하도로는 폐쇄적인 공간 구조와 내·외부 조도 차이로 인해 지상도로와 다른 교통 환경을 형성하며 이러한 특성은 교 통사고에 영향을 미칠 수 있다. 특히 고속도로 터널에서 사고 발생 시 대형 인명 피해로 이어질 가능성이 크다는 점을 고려할 때 지하도로에서도 유사한 우려가 제기된다. 따라서 지하도로의 교통류 특성을 면밀히 분석하여 안전성을 평가하 고 사고 예방을 위한 효과적인 대책을 마련하는 것이 중요하다. 본 연구에서는 서부간선 지하도로 성산 방면의 14개 VDS 검지기 데이터를 기반으로 지점별 속도 변동성과 교통사고 분석을 통해 안전성을 평가하였고 분석 결과의 시사점 을 바탕으로 지하도로 속도 관리 전략을 설계하였다. 먼저, VDS 검지기 지점별 속도 표준편차와 time-varying-volatility 산출 및 속도의 변동성과 교통사고 데이터 매칭을 통해 사고 개연성과 심각도를 분석하였다. 이후, 사후검정을 통해 속 도 및 속도 변동성 기준으로 동질적 부분집합을 도출하고 회귀분석을 통해 속도 변동성과 교통량·밀도 간의 관계를 규명 하여 속도 변동성을 최소화할 수 있는 최적의 교통량과 밀도를 산출하였다. 분석 결과, 속도 변동성이 큰 구간에서 사고 개연성과 심각도가 높게 나타났으며 지하도로에 구간단속을 적용할 경우 하류부에서 변동성이 증가하는 현상을 확인하 였다. 이를 바탕으로 위험 구간을 식별하고 해당 구간에 가변형 속도 제한 시스템을 적용한 로컬 속도 관리 전략을 제시 하였다. 본 연구의 결과는 지하도로의 사고 예방 및 안전성 향상을 위한 실질적인 속도 관리 전략 설계에 기여할 수 있 을 것으로 기대된다.

This study aims to calculate the passenger car equivalent (PCE) of heavy vehicles on one-lane exit sections of underground roads. Traffic-flow simulations were performed using the VISSIM software program. The scenarios were designed under varying conditions, including design speeds of 40 and 50 km/h, slope gradients ranging from 3% to 9%, and heavy vehicle proportions between 5% and 40%. The mixed-traffic flow capacity was calculated for each scenario at the threshold levels, and the PCE was estimated based on the two capacity conditions. The results revealed that the PCE decreased at lower design speeds. For slopes less than 6% at a design speed of 40 km/h, and for slopes less than 4% at 50 km/h, the PCE remained consistent across all conditions. Single-lane exit sections are often employed on underground roads because of congestion and structural constraints. However, when heavy vehicles are present in these sections, the overall traffic flow is dictated by the speeds of the heavy vehicles. To address this issue, the implementation of variable or temporary two-lane exit sections has been proposed to enhance traffic flow and capacity.

전 세계적으로 지하도로의 건설이 활발히 이루어지고 있지만, 지하도로에서의 운전자 행태에 대한 연구는 여전히 부족한 실정이다. 또한 현재 지하도로 설계기준은 주로 지상도로나 터널 기준을 준용하고 있어, 지하 특유의 환경적 요인을 충분히 반영하지 못하고 있 다. 이에 따라, 지하도로에서의 운전자 행태를 분석하고 이를 반영한 설계기준 마련이 필요하다. 본 연구는 지하도로에서 운전자가 차로 변경을 어떻게 수행하는지 분석하고, 정보 제공 방식이 운전자 행태에 미치는 영향을 평가 하는 것을 목적으로 한다. 이를 통해, 향후 지하도로 설계 및 운영에 필요한 개선 사항을 제안하고자 하였다. 이를 위해 본 연구에서 는 소형차 전용도로의 설계 재원을 기준으로한 VR 기반 주행시뮬레이터 맵을 구성하였고 34명의 피실험자를 모집하여 주행시뮬레이 터 실험을 수행하였다. 첫 번째로 차로변경 행태를 살펴보기 위하여 현행 차로 변경 허용 구간 기준인 400m와 대안으로 차로 변경 허용 구간 2km로 비교하 여 운전자의 차로변경 행태에 대해 분석을 수행하였다. 두 번째로는 현행 정보제공 체계 기준인 분기전 2km, 1km, 150m 전 정보안내 대안과 대안으로 추가 500m 지점에 정보를 제공하는 방안에 대해 주행시뮬레이터 실험을 수행하고 대안별 효과를 비교하였다. 실험결과를 검토한 결과, 지상 도로보다 지하 도로에서 운전자들은 차로 변경을 더 어려워하는 경향이 있었다. 두 번째로 운전자들은 차로 변경 허용구간에 따른 주행패턴의 유의미한 변화는 존재하지 않는 것으로 나타났으며, 평소의 주행 습관에 따라 차로 변경을 하 는 것으로 나타났다. 세 번째로는 정보 제공 횟수를 늘릴 경우 운전자들은 차로 변경과 진출 지점을 더 빨리 결정하며, 차로 변경 지 점의 분포가 작아지는 현상이 관찰되었다. 이는 많은 운전자들이 비슷한 지점에서 차로 변경을 하게 되어 상충 구간이 줄어들고, 그에 따라 교통 안전성이 증가할 수 있음을 의미한다.

PURPOSES : The purpose of this study is to identify the causes and expected problems of traffic flow in connection with ground roads that are expected to become stagnant owing to the increase in underground road infrastructure, and to derive methods to solve the problem in the future. METHODS : The basic design of underground roads is similar to that of tunnels. However, there is a point where the slope is large as the entering and exiting sections move underground. The ability of a heavy vehicle to assume a mound may vary depending on the slope. Therefore, in this study, a connection path section with a long slope was constructed using VISSIM, a simulation program, and it was verified whether analysis related to the slope and heavy vehicles in an underground road can be performed in the simulation. Subsequently, an analysis was conducted by setting a scenario and an effect index. In particular, this study analyzes internal delay patterns in the event of an unexpected situation on an underground connection road by performing shock wave analysis to analyze speed reduction according to heavy vehicles and slopes. RESULTS : A correlation between the slope of the underground road and decrease in the average speed according to the increasing rate of heavy vehicles was established. It was also possible to analyze the maximum length and duration of the delay connected to the rear in the event of a delay in the underground road and the shock wave speed transmitted to the rear. The analysis showed that the rate of increase in problems owing to delays ranged from 5% to 20% for the ratio of heavy vehicles. In particular, all effect scales increased significantly at a 9% slope. CONCLUSIONS : This study analyzes the causes of land congestion (slope and heavy vehicle mixing rate), which can be a major problem in underground roads in the future. In the future, by establishing lane-specific speed control strategies and lane control strategies based on this study, it will be necessary to derive solutions such as introducing traffic safety on the underground road by minimizing the shock wave delivered to the rear by providing information on traffic communication conditions inside the underground road to individual vehicles.

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 : 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.