It is common practice to assign revenue to accomplish specific governmental tasks in general, and to provide transport infrastructure in particular. However, neither the literature in public administration nor in public choice has reached a consensus about the effects that earmarking has on efficiency. Building on earlier public choice models, we argue that this mechanism prevents budget debates from occurring and reduces the incentives for ministers to monitor the colleagues whose budgets are financed by earmarked revenues. These latter tend to overuse public resources, thus increasing inefficiency. We used a stochastic frontier model fed with data from Swiss cantonal ministries of transport from 2000 to 2016 to test this hypothesis. Our results revealed a negative effect of earmarking on efficiency. For every 1,000 additional Swiss francs per capita financed out of an earmarked fund, the input requirement increases by 5.4 percent on average.