Historically, road vehicle operatingcosts have tended to dominate highway economic appraisals indeveloping countries, due to the poor road surfaces that canoccur there. The operating costs of railways and ports arealso substantial, and form key components of cost benefitanalyses of their associated infrastructure. The definitionof operating costs for Bank projects is therefore importantin obtaining a reliable economic appraisal. In this Note,Section 1 introduces the key issues associated withoperating costs, whilst the following sections discuss thecomponents and sources of operating costs by mode. Roadvehicle operating costs are presented in Section 2, railwayoperating costs in Section 3, and port operating costs inSection 4.