KOREASCHOLAR

PURPOSES: The objective of this study is to analyze the effect of superelevation on the existing local freeway ramps where occurrence of traffic incidents are concentrated in order to improve the safety of ramp curves. Using a superelevation slope test conducted on Cheong-ju interchange as a case study, operating speed and lateral friction coefficients are measured, and the safety before and after increasing the superelevation is analyzed.
METHODS: First, the actual operating speed of freeway ramps is measured for analysis and the 85th-percentile speed is calculated. This is followed by a measurement change in the lateral friction coefficient because of an increase in superelevation slope from 6% to 10%. Based on the change in lateral friction coefficient, an evaluation of the safety of driving mechanics is carried out and suggestions for the most appropriate superelevation slopes are presented.
RESULTS: The operating speed (V85) of the loop ramp increases by up to 5.6 km/h after increasing the superelevation slope, and the operating speed (V85) of reverse ramp curve increases by up to 6.1 km/h. However, the standard deviation of the speed between each section has decreased, making it easier to drive smoothly. Although some sections of the loop ramp show poor safety due to the difference between actual and design friction coefficients in the safety evaluation before the increase of superelevation slope, the lateral force decreases after the increase of superelevation slope, improving the safety of the road.
CONCLUSIONS : Currently, Korea’s freeway ramps pose a safety risk to vehicles traveling at speeds higher than the design speed. To improve the safety of freeway ramps, analysis on the effect of increase in superelevation slope found that the lateral friction coefficient decreases, which in turn improves the safety of freeway ramps.

ABSTRACT
 1. 서론
  1.1. 연구의 배경 및 목적
  1.2. 연구의 내용 및 방법
 2. 기존 문헌 고찰
 3. 연구 방법론
  3.1. 분석구간 설정
  3.2. 주행속도 측정
  3.3. 횡방향마찰계수 산출
  3.4. 도로 안전성 평가
 4. 분석 결과
  4.1. 주행속도 측정 결과
  4.2. 횡방향마찰계수 산출 결과
  4.3. 횡방향마찰계수를 통한 도로 안전성 평가 결과
 5. 결론 및 향후 연구과제
 REFERENCES

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• 김정민(한국교통연구원) | Kim Jeongmin 교신저자
• 정승원(서울시립대학교 교통공학과) | Jeong Seungwon
• 최재성(서울시립대학교 교통공학과) | Choi Jaisung
• 김상엽(전북연구원 지역개발연구부) | Kim Sangyoup