What are the limitations of using purely mechanistic-empirical pavement design methods without considering local performance data?

Mechanistic-empirical (M-E) pavement design methods use engineering mechanics principles to calculate stresses and strains within a pavement structure under traffic loading, and then relate these calculated responses to observed pavement performance through empirical relationships. While M-E methods are more sophisticated than purely empirical methods, they still have limitations when applied without considering local performance data. A key limitation is that the accuracy of M-E predictions depends on the accuracy of the input parameters, such as material properties (e.g., elastic modulus, Poisson's ratio) and traffic loading. If these inputs are not representative of local conditions, the predictions can be inaccurate. M-E models often rely on simplified assumptions about material behavior and environmental factors. For example, they may not fully account for the effects of moisture damage, freeze-thaw cycles, or long-term aging of materials. Local performance data provides valuable information about how pavements actually perform under specific conditions. This data can be used to calibrate and validate M-E models, improving their accuracy and reliability. Without local calibration, M-E models may over- or under-predict pavement distresses, leading to incorrect design decisions. Local factors such as construction practices, material availability, and maintenance strategies can also significantly influence pavement performance. These factors are difficult to incorporate directly into M-E models, but they can be accounted for through local calibration using performance data. Moreover, M-E models may not be able to capture all of the complex interactions between different distress mechanisms. Local performance data can help to identify these interactions and improve the understanding of pavement behavior. Simply put, M-E design provides a theoretical framework, while local performance data provides the real-world validation needed to ensure accurate and reliable pavement designs.