Pavement friction under wet conditions is a critical factor affecting driving safety and is determined significantly by water-film thickness (WFT). Although current road geometric design standards incorporate wet-pavement friction coefficients as design parameters, they do not adequately account for the effects of WFT. This study estimates the variation in the coefficient of friction caused by changes in the WFT and applies the results to the calculation of stopping sight distance (SSD) and radius of curvature (RC), which are essential elements in road geometry design. Through this approach, the study identifies the limitations of current standards and proposes potential improvements. WFT was estimated using the Gallaway model, which was previously verified through comparative analysis and experimental validation. The model incorporates key influencing factors such as rainfall intensity, pavement slope, drainage path length, and mean texture depth. Based on the estimated WFT, the longitudinal and lateral friction coefficients were calculated using Gallaway’s SN and Lamm’s models, respectively. Using these friction values, the SSD and RC were evaluated under various pavement and environmental conditions. Furthermore, comparisons with existing design guidelines were performed to assess whether the predicted values satisfy the standards under different conditions. Additionally, areas requiring improvement were identified. The analysis confirmed that WFT increases with rainfall intensity and drainage path length, whereas it decreases as the pavement slope, mean texture depth, and tread depth increase. An increase in the WFT significantly reduces the friction coefficient, which consequently increases the SSD and required RC. In particular, under conditions such as heavy rainfall, worn treads, long drainage paths, and shallow surface textures, the calculated SSD and RC typically exceed the minimum requirements of current road-design standards. By contrast, ensuring sufficient surface texture effectively maintains friction performance and mitigates increases in the SSD and RC. The findings of this study suggest that current road-design standards—based on dry or vaguely defined wet conditions—may not sufficiently address the effects of WFT on pavement friction. A quantitative, WFT-based approach is required for more realistic friction estimations. To enhance safety in rainy conditions, road designs should incorporate structural and material improvements, such as optimizing pavement slopes, reducing the drainage path length, maintaining adequate surface texture and tread depth, and adopting high-performance surfacing materials. Additionally, dynamic speed-management systems during rainfall and preventive maintenance for sections with inferior drainage should be considered to improve driving safety under wet weather conditions.

ABSTRACT
1. 서론
2. 이론적 배경
    2.1. 노면 마찰력 특성
    2.2. 수막두께 예측에 관한 기존 모델
    2.3. 마찰계수 예측에 관한 기존 모델
    2.4. 정지 시거 산정 방법 및 현행 기준
    2.5. 곡선 반경 산정 방법 및 현행 기준
    2.6. 수막현상에 따른 마찰계수 변화와 현행 도로 설계기준의 한계
3. 아스팔트 포장 노면의 수막두께 및 마찰계수산정
    3.1. 수막두께 예측 모델 선정을 위한 문헌 검토
    3.2. 마찰계수 산정을 위한 변수 및 범위 설정
    3.3. 강우 조건 및 도로 기하구조 조건에 따른 마찰계수예측 결과
    3.4. 도로 기하구조 설계 시 적용되는 최소 마찰계수기준과 본 연구의 마찰계수 예측값 간 비교
4. 본 연구에서 산정한 정지 시거 및 곡선 반경과기존 기준 비교
    4.1. 정지 시거 및 곡선 반경 산정 개요
    4.2. 정지 시거 산정 결과 및 기준과의 비교
    4.3. 곡선 반경 산정 결과 및 기준과의 비교
5. 결론
감사의 글
REFERENCES

• 최예인(강릉원주대학교 토목공학과 박사과정) | Choi Ye In
• 김영규(강릉원주대학교 스마트인프라연구소 연구교수, 공학박사) | Kim Young Kyu
• 이승우(강릉원주대학교 스마트인프라공학부 교수, 공학박사) | Lee Seung Woo Corresponding author