Evaluation of pavement condition index and aging using spectroscopy analysis of asphalt samples and Sentinel-2 satellite images (Case Study: Sabzevar- Shahrood Road)

Predicting the budget for road construction and maintenance has been one of the most significant issues in government budget allocation. Early identification of road problems through preventive measures increases their lifespan and reduces maintenance costs. This study focuses on a 35-kilometer stretch of the Sabzevar-Shahrood road, located in a hot and dry region and serving as a transit path from east to west, where asphalt damage is frequently observed. To forecast the Pavement Condition Index (PCI) based on pavement age (AGE), systematic random sampling of asphalt was conducted at designated locations using GPS, followed by spectral analysis in a physics laboratory with a spectrometer. Optical images from Sentinel-2 were processed, utilizing green, blue, red, and near-infrared bands due to their 10-meter resolution and wavelengths ranging from 440 to 900 nanometers, which correspond closely to the asphalt response spectrum. Subsequent analyses involved extracting pixel values from the corresponding bands at the asphalt sampling sites within the Sentinel-2 satellite images and conducting statistical evaluations. The inverse relationship between AGE and PCI indicates that field analyses and calculations of distress indices were performed accurately, with their extension in band analysis as dependent variables being appropriately selected. In examining the relationship between the PCI and satellite imagery spectroscopy for predicting distress indices, the near-infrared band (B8) exhibited superior performance with a coefficient of determination (R2 = 0.48) compared to other bands, demonstrating relatively high accuracy that can be extended to other distress indicators such as the Pavement Serviceability Index (PSI). Given the average spatial resolution of 10 meters for the selected bands from Sentinel-2, a relatively low convergence coefficient  (R=0.323) was observed in this analysis concerning pavement distress dimensions. Furthermore, in assessing the relationship between pavement age (AGE) and satellite imagery spectroscopy for predicting pavement age, the near-infrared band (B8) outperformed other bands with a coefficient of determination R2= 0.55. In this analysis, higher convergence coefficients (R=0.56) were noted, suggesting that higher wavelength numbers in spectroscopy indicate younger pavement conditions. Traffic load significantly influences pavement distress; additionally, employing existing criteria for random sample selection plays a crucial role in determining distress indices and final analytical outcomes. Therefore, Sentinel-2 satellite images in the near-infrared band with a resolution of 10 meters demonstrated better correlation with age and distress indices of roads. However, these images will perform more effectively on roads wider than 10 meters.
In examining the relationship between the PCI and satellite imagery spectroscopy for predicting distress indices, the near-infrared band (B8) exhibited superior performance with a coefficient of determination (R2 = 0.48) compared to other bands, demonstrating relatively high accuracy that can be extended to other distress indicators such as the Pavement Serviceability Index (PSI). Given the average spatial resolution of 10 meters for the selected bands from Sentinel-2, a relatively low convergence coefficient (R=0.323) was observed in this analysis concerning pavement distress dimensions. ،he near-infrared band (B8) outperformed other bands with a coefficient of determination (R2= 0.55). In this analysis, higher convergence coefficients (R=0.56) were noted, suggesting that higher wavelength numbers in spectroscopy indicate younger pavement conditions. Traffic load significantly influences pavement distress; additionally, employing existing criteria for random sample selection plays a crucial role in determining distress indices and final analytical outcomes. Therefore, Sentinel-2 satellite images in the near-infrared band with a resolution of 10 meters demonstrated better correlation with age and distress indices of roads. However, these images will perform more effectively on roads wider than 10 meters.