Resumen: We present a method oriented to determine indicators representing different dimensions of users' travel time, such as in-vehicle time and its variability. We focus the service level measurement on users, but not their subjective perception, since we build the indicators from objective data. We apply the method to six Latin American cities, which shows the method's flexibility to fit different available information collected from sources such as in-field measurements or electronic control systems for bus operations. The method's core is the selection of a representative sample of trips. We estimate the service level based on different variables (e.g., speed, frequency, travel time, and waiting time) for every sampled trip. The contribution of this work is the design and implementation of a methodology for service level evaluation. As a byproduct, we compare public transportation systems' levels of service in the studied cities.