This article presents new methodology for assessing the quality provided by urban surface transit systems in terms of comfort, speed and coverage. A set of robust indicators are presented to measure how transit supply serves the multimodal chain of users (access, waiting and in-vehicle time) as well as the performance of the transit system. These measures are summarized in a unique indicator that accounts for the quality of the global service. The latter may be a useful tool to redefine existing transit systems (routes, frequencies or capacity allocation) to any changes in the spatial or time distribution of demand. This methodology has been implemented to the local bus network in Barcelona (Spain) in order to identify the necessary readjustments between transit supply and demand.