This study tested the effect of introducing moving-block signaling on the technical efficiency of urban metro rail systems. The study used a panel data set of 27 urban metro systems across 20 countries for 2004 to 2012. When moving-block signaling was considered as a treatment, the effect of the associated benefits on output efficiency levels was able to be measured. Stochastic frontier analysis was employed to estimate technical efficiencies for each metro, and then propensity score matching was applied to evaluate the effect of the type of signaling on technical efficiency. The study allowed the selection of appropriate reference groups and accounted for confounding factors. The study is novel in its provision of empirical evidence of this nature. The results indicate that the technical efficiency of a metro can be improved by 11.5%.