This chapter first provides an overview of the current state-of-the-art reliability assessment approaches, including testing and probabilistic data analysis approaches, for vehicle components and systems, vehicle exhaust components and systems. The challenges and opportunities in the reliability assessments are also identified. Subsequently, several recently developed new concepts and methodologies are provided with an emphasis on fundamentally understanding the relationship among various reliability assessment methods with a unified view. These new concepts include a fatigue S-N curve transformation technique and a variable transformation technique in a damage-cycle f P ( P ) https://s3-euw1-ap-pe-df-pch-content-public-u.s3.eu-west-1.amazonaws.com/9780429488009/93b4516f-d45a-49b1-9fe4-b0856f853e1a/content/equ_1561.tif"/> diagram. These two transformation methods are best suitable for reliability assessment of vehicle components. With these new concepts and methodologies, the current S -N data analysis and testing methods can be interpreted in a new unified probabilistic framework with much ease and flexibility in usage. The importance of selecting a probabilistic distribution function in probabilistic data analysis is emphasized. The potential benefits of using Bayesian statistics approach with small sample size in cost reduction and accuracy improvements are also addressed. Finally, the basic reliability assessment approaches for systems are provided. The effectiveness of these new concepts and methodologies are demonstrated with pertinent examples.