Inland vessels at sea: a useful contradiction to solve missing links in waterway systems

For a limited number of maritime ports, the local regulations conditionally allow inland vessels to carry out short sea voyages to reach the inland waterway network. This type of traffic, usually referred to as 'estuarine', 'fluvio-maritime' or 'sea-river' traffic, is well established in e.g. Zeebrugge, Le Havre, the Italian Adriatic coast. Inland vessels have to fulfil a set of technical requirements, issued by both the classification society and the local authorities, while they can only navigate at sea in favourable weather conditions. An overview is given of the regulations valid for the different areas where river-sea traffic is common practice. Apparently, no uniformity exists among neither the requirements nor the restrictions.