PURPOSES : The purpose of this study is to derive specific road design elements for safe urban underground and to adopt measures for minimizing traffic delays and to maintain efficient operation.
METHODS : In this study, a qualitative study was conducted using Focus Group Interview (FGI) method to identify significant connection characteristics and develop connections to urban underground roads. Finally, this study analyzes design elements necessary for traffic safety and efficient traffic operation. In addition, relevant case studies were performed with keywords from the FGI method results. Therefore, major design elements were analyzed for urban underground road connection and connection analysis for traffic simulation-based verification.
RESULTS : The main characteristics of the connection between the underground roads of the downtown area were divided into three types: traffic flow characteristics, geometric characteristics, and driver behavioral characteristics. From the review of 16 leading studies (10 domestic papers and 6 international papers) according to the characteristics, the main design factors for “traffic flow characteristics” include the traffic volume, design speed, heavy vehicle ratio, and lane change. The important design elements for “geometric characteristics” include the separation distance, number of lanes, slope, lane and shoulder width and the design factors for “driver behavioral characteristics” showed reaction time, driver vision, and driving speed. CONCLUSIONS : The FGI method identified the main characteristics of connections to the underground roads. In addition, the relevant empirical and theoretical research data were considered in case studies, and the design elements were derived and separated spatially based on the features of each design element, establishing a point-specific design element guideline.

ABSTRACT
1. 서론
2. 연구수행방법
3. FGI 분석을 통한 질적연구 수행
    3.1. FGI 분석 개요
    3.2. FGI 분석 관련 문헌고찰
    3.3. FGI 조사내용
    3.4. FGI 분석 결과
4. FGI를 반영한 사례연구 및 설계요소 도출
    4.1. 사례연구 수행
    4.2. 주요 설계요소 도출
5. 결론
REFERENCES

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