The present article outlines the risk factors affecting voyage efficiency in tramp shipping operations. The influence of factors of time and costs parameters is identified. The voyage revenue is formulated and studied according to variances of time and costs elements. For the evaluation of efficiency of voyage operations an approach based on value-at-risk method is proposed and voyage statistics in short sea shipping are studied. The results presented prove the applicability of the method for efficiency evaluation of tramp shipping operations and voyage planning.