Lots of studies have been devoted to shipper's modal choices since Baumol and Vinodt (1970) seminal papers. But, surprisingly, whereas institutional aspects play a determinant part in the structure of relationships in every supply chain, they are barely taken into account in academic papers (McGinnis, 1989; Jiang, 1998; Henscher and Puckett, 2005; Brooks et al., 2012), particularly regarding transaction costs. Indeed, shippers' modal choices are often characterised by their inertia (Golicic et al, 2003), which cannot be explained without Transaction Costs Economics (or New Institutional Economics, see Ruester, 2010), as developed by Coase (1937) and Williamson (1985; 1996) seminal works. This paper aims at showing that transaction costs are partially responsible for the low modal share of container barge transport in French maritime ports (9% of TEU in Le Havre and 5% in Marseille in 2007). But instead of dealing with the transaction chain of container barging itself (Fischman and Lendjel, 2012), the paper focuses on shipper's decision making process. The paper finds empirical evidence of those costs in ECHO's survey (Guilbault et al., 2008), focusing on shipments involving barging legs in containerized maritime chains. The last section discusses those results.