Formal models for the safety validation of autonomous vehicles have become increasingly important. To this end, we present a safety framework for longitudinal automated driving. This framework enables the calculation of minimum safe inter-vehicular distances for arbitrary ego vehicle control policies in a computationally efficient manner. We use this framework to enhance and generalize the Responsibility-Sensitive Safety (RSS) [1] model and models based on it, which fail to cover situations where the ego vehicle has a higher decelerating capacity than its preceding vehicle. © 2024 IEEE.