Machine learning-based remote PPG signal quality assessment for in-vehicle driver monitoring

• First systematic evaluation of ML and DL for in-vehicle rPPG quality classification. • Peak-centered magnitude spectrum enhances rPPG quality classification. • XGBoost with five frequency–domain features achieves AUC 0.86 while keeping computational efficiency low. • Real-world validation on 31 drivers under varied driving scenarios. Camera-based vital signs monitoring is emerging as a key component of intelligent transportation systems, enabling unobtrusive driver health tracking to enhance road safety. Remote photoplethysmography (rPPG), a technique enabling this camera-based monitoring, allows pulse rate estimation; however, its use in vehicles is susceptible to motion artifacts and dynamic lighting conditions, limiting its reliability. To address this, we evaluated various machine learning (ML) and deep learning (DL) techniques for rPPG signal quality classification, including extreme gradient boosting (XGBoost), support vector machines, convolutional neural networks, and long short-term memory. Through a rigorous comparison of time and frequency domain representations, we reveal that the peak-centered magnitude spectrum markedly enhances the ability to distinguish reliable from unreliable rPPG segments, surpassing traditional time-domain approaches. Notably, our XGBoost model, leveraging the top five frequency-domain features, not only achieved superior performance (AUC of 0.86, with strong sensitivity) compared to existing state-of-the-art PPG quality classification methods on our dataset, but also demonstrated vastly lower computational cost quantified by floating-point operations per second. To our knowledge, this is the first study to systematically investigate ML and DL approaches for rPPG signal quality classification, particularly within a real-world automotive context. These findings pave the way for integrating robust, computationally efficient driver health monitoring into advanced Driver Monitoring Systems and next-generation remote health monitoring technologies.