The objective of the article is to develop and to substantiate adequacy of the proposed indicator for assessing availability of rolling stock for urban mass transit or urban passenger transport (UPT). As such an indicator, it is recommended to use a calculated indicator: a conventional one-hundred-seat vehicle. The currently used indicators characterising provision of UPT with vehicles, consider only the physical number of the latter. This does not provide an assessment of carrying capacity of UPT, considering the existing operating conditions (real operating speeds on the routes of UPT, the existing level of the coefficient of the fleet being used on the routes as compared to the total number of fleet units, etc.). The proposed indicator of availability of the rolling stock considers not only the natural number of vehicles, but also their passenger capacity, the indicated significant technical and operational indicators of the vehicle fleet. The basis for assessing the carrying capacity of the rolling stock fleet is a conventional one-hundred-seat bus, which performs transportation on routes with an average operating speed. For real buses, this basic unit is adjusted in accordance with real travel speeds and the prevailing values of technical and operational indicators. A similar adjustment is performed for real trolleybuses and tram cars, which makes it possible to level the operational differences in the rolling stock of various types of UPT to compare them in terms of carrying capacity.The methodology used in preparation of the article is based on the integrated use of scientific knowledge in the fields of applied science on operation of transport, statistics (statistical observation and accounting of the work of UPT), a comparative analysis of indicators used in various industries, in particular, in agriculture to assess the level of provision with the main production vehicles (conventional tractor), benchmarking research and development of Russian and foreign authors on the problem of improving operation of UPT.The indicator is intended for use in development and assessment of the level of implementation of programs for development of UPT and the urban environment, analysis of the quality of transport planning and services provided to passengers, comparisons of provision with vehicles in different cities.