Thus far in Vietnam, two urban railway lines have been built in Hanoi, of which the Cat Linh - Ha Dong line has been in operation since November 2021. The elevated section of the Nhon - Hanoi Station line (from Nhon to Cau Giay) has been put into operation since August 8, 2024. In Ho Chi Minh City, the Ben Thanh - Suoi Tien line is also being urgently completed and expected to be exploited by the end of 2024. Urban railway projects in Vietnam are all built by foreign contractors and then handed over to Vietnam for exploitation. Assessing the reliability of the entire system in general and of rolling stock in particular during the operation of urban railways in Vietnam is a completely new and unresearched issue. The article presents some research results on evaluating the reliability of rolling stock operating on the Cat Linh - Ha Dong urban railway based on data collected from the commencement of operations on November 6, 2021, to March 31, 2024, and the CL-HD-RS-RAMS software developed by the authors.