國際糙度指標 (IRI) 具檢測成本低與高效率之優勢，為廣泛採用之鋪面平整度指標。然而，IRI主要反映整體縱向平整度，對於快速公路伸縮縫周邊產生之局部破壞、車轍或裂縫，其作為初步警示指標之適用性仍有進一步檢視與探討之空間。為探討提升養護效率之可能性，本研究以台86線快速公路「含伸縮縫路段」為對象，探討是否能透過IRI資料，輔助辨識最大車轍深度偏高之潛在需優先檢視路段。本研究整合台86線2016至2025年歷年IRI資料、伸縮縫種類，及2026年裂縫率與最大車轍深度橫斷面資料，以100公尺檢測單元為分析尺度。首先運用重複量數ANOVA與單因子ANOVA，檢視歷年IRI與不同伸縮縫種類之統計差異。隨後基於預防性養護考量，採用Z標準分數 (Z Score) 將指標轉換為相對尺度，以Z Score大於1作為探索性篩選門檻，交叉分析IRI劣化時是否伴隨裂縫擴大或車轍加深。分析結果顯示，於台86線快速公路之研究範圍內，IRI或可作為觀察長期平整度變化之參考，惟不同伸縮縫種類之IRI表現未呈一致趨勢，尚不宜據此評斷材料優劣。經Z Score交叉檢視觀察到，最大車轍深度相對偏高之路段，其IRI亦呈現上升趨勢。數據指出，當樣本最大車轍深度達12.65 mm時，對應之IRI平均值約升至2.56 m/km。基於探索性分析，本研究初步建議實務上或可考慮將「IRI達2.56 m/km」與「最大車轍深度達12.65 mm」納入雙重條件，視IRI為限縮需優先檢視區段之輔助工具；若同時符合此條件，建議可評估優先列為現地檢測之對象。;The International Roughness Index (IRI) is a cost-effective pavement smoothness indicator， but its use as a preliminary warning for localized distress around expressway expansion joints warrants further exploration. To enhance maintenance efficiency， this study evaluates the use of IRI to identify sections on Provincial Highway 86 with elevated rut depths that may require prioritized inspection. Using historical IRI data (2016-2025)， joint types， and 2026 cross-sectional distress data within 100-meter inspection units， the study employed ANOVA to assess statistical differences. Furthermore， a Z score > 1 was used as an exploratory threshold to cross-analyze whether IRI deterioration corresponds to increased cracking or rut depth. Results indicate that， within Provincial Highway 86， IRI performance across joint types shows no consistent trend， making it unsuitable for judging material superiority. However， cross-examination reveals that sections with relatively high maximum rut depths exhibit an upward IRI trend. When the maximum rut depth reaches 12.65 mm， the average IRI increases to approximately 2.56 m/km. Based on this exploratory analysis， this study preliminarily suggests adopting "IRI ≥ 2.56 m/km" and "maximum rut depth ≥ 12.65 mm" as dual criteria. IRI can serve as an auxiliary tool to narrow down sections requiring prioritized inspection， and locations meeting both conditions may be prioritized for on-site inspections.
