This paper investigates the capability of the Moment-Ratio Diagram (MRD) to model and evaluate travel time reliability. The MRD is a sample-based graphical tool associated to the Halphen distributions, a class of three flexible probability density functions. From empirical data, the MRD enables a selection of the appropriate Halphen distribution. The main contribution of this paper is to provide an assessment on how the MRD coordinates are relevant as reliability metrics. Two empirical data sets are used: the first one was collected with a License Plate Recognition technique near Lyon (France), while the second one is constituted of Bluetooth measurements on an arterial corridor in Portland, Oregon (USA). A comparative study is undertaken with a set of classic reliability indicators. The different results highlight strong statistical correlations between MRD coordinates and well-known travel time metrics used here as a proxy for travel time reliability. The main finding is that the MRD coordinates appear as consistent reliability metrics and the MRD as a useful tool for network managers.