Minimum energy expense and maximum safety with some comfort characterizes the definition of ideal human mobility. Recent technological advances in the autonomous vehicle driving systems not only enhance the safety and/or comfort levels but also present a significant opportunity for automated eco-driving. In this regard, a longitudinal controller for a smart and green autonomous vehicle (SAGA) is investigated. In principle, it is an eco-adaptive cruise control which aims at minimizing energy expenditure and maximizing energy regeneration. This paper presents detailed energy and powertrain analysis through the simulation of specific SAGA application concepts such as, dynamic programming-based offline acceleration optimization for a battery electric vehicle, or SAGA as a supervisory controller in combination with equivalent consumption minimization strategy for a hybrid electric vehicle. The main focus is on the evaluation of a vehicle energy manager which autonomously controls the longitudinal motion while actively balancing efficiency and safety. The comfort is not directly addressed in the conception but regarded as a quality criterion.