The specific aims of this study are: 1) to examine the feasibility of providing children with disabilities to explore the environment with a modified ride-on car; 2) to quantify whether children with disabilities are able to have more social interactions with a ride-on car; 3) to examine the progression of socialization to determine which factors might influence the learning curve during intervention and follow-up phases; 4) to compare the effectiveness of using the modified toy cars through the hospital-based program and regular therapy program to determine the critical factors on increasing independent mobility and socialization after intervention and follow-up phases, including motivation, treatment executor, treatment environment and play programs. Through the comparison of Car Play (i.e., play with the use of toy cars) and Natural Play (i.e., play without the use of toy cars), investigators hypothesize that children with disabilities are able to learn how to drive the modified toy cars in the hospital-based group. They will have increased socialization (i.e.,self-initiated contacts, vocalizations, positive facial expressions) when driving the cars than the regular therapy program, i.e., control group.