Introduction: Public transit is a sustainable transport mode that can improve the health and well-being of urban population. Following the development of mass rapid transits (MRT) in Greater Kuala Lumpur, this study aims to em- pirically test the behavioral framework behind the intention to use rail transport among private motor vehicle users. Methods: Data was obtained through a cross sectional travel survey (N=509) conducted on the catchment popula- tion of an upcoming MRT line in Greater Kuala Lumpur. The factors in the hypothesized framework were service quality, environmental health concerns, attitude and the intention to use. The data was modeled using the Maximum Likelihood (ML) estimation in structural equations. Results: The validated model indicated that service quality and environmental health concerns significantly affected respondents' intention to use rail transport, mediated by attitude. Reliability, convenience and comfort were the most valued service qualities, while environmental concerns were more valued than health concerns. There were significant moderation by age, income, and having children below 18 years old on the framework. Higher age groups valued more on service quality, while attitude had larger determin- ing effects on the higher income groups. Besides, the lower direct effect of service quality on attitude among higher income groups implied possibility of other affective factors for the subgroup. Conclusion: This study demonstrated the importance of service quality, attitude, and environmental health concerns in encouraging rail transport usage among private motor vehicle users. Certain subpopulations may be targeted for promotion strategies to improve rail transport use in the city.