This paper deals with a novel patronage ramp-up analysis model. The ramp-up effect represents the delay in ridership take-up during the first periods of new transport services or facilities. This influence is known as one of the external errors of transport demand forecasts, which degrades the reliability of demand studies and economic appraisal for transport schemes. Traditionally, professional judgment and regression analyses have been used to investigate this effect, but the existing methodologies suffer from the inherent limitations of being biased and arbitrary. In this paper, a heuristic F-test is suggested as an alternative framework. The model proposed is tested with road and rail schemes of South Korea. The case studies illustrate the ability of the model to find the ramp-up parameters involving the duration and the ratio of this effect. Subsequently, a numerical example of cost-benefit analysis including ridership ramp-up is provided. The experiment shows that incorporating the ramp-up effect could provide help for more cautious decision making during the appraisal. A summary and future directions of the study are also provided.