The whole study duration will be 18 weeks, including 9-week intervention and 9-week follow-up; the total amount of treatment will be equal for two groups. The hospital-based program will be administered by the therapist and include 120 minutes/per session, 2 sessions/per week. In addition, the research team will visit the hospital once/per week to provide assessments. The regular therapy group will continue their regular therapy without any additional car driving training. The research team will visit them once/per week for the assessments. The assessments include behavior coding from the videotapes and the clinical assessments. The findings of this study will help to understand the feasibility and effectiveness of using the low-tech modified toy cars on advancing children's mobility and socialization. They can be used in the clinics and are a low cost alternative or addition to other mobility devices. They may provide a novel therapeutic tool to improve mobility, socialization and development.