With advancements of communications and vehicle technologies, mobility on demand becomes an important issue to enhance public transportation and to provide more flexible service. The Dial-a-Ride Problems (DARP) is one of the traditional transportation services of mobility on demand. The objective of standard Dial-a-Ride Problem (DARP) is to minimize total travel cost. However, most of DARP applications are designed for disabled and elderly people to provide more convenient and friendly services. Thus, the profit or operational cost should not be the only consideration. In addition to travel cost, the objective functions should include service quality and eco-efficiency. In order to consider three conflicting objectives simultaneously, the speed level constraints are added to the model. We defined a set of speed levels, and these constraints ensure that only one speed is selected for each arc. Mathematical models are described for each objective and computational experiments are performed on realistic instances.