Judgment of the Court (Fifth Chamber) of 5 October 1993 in Joined Cases C-13/92, C-14/92, C-15/92 and C-16/92: (references for preliminary rulings from the College van Beroep voor het Bedrijfsleven): Driessen en Zonen V. o. f. and Others v. Minister van Verkeer en Waterstaat (Structural improvements in inland waterway transport — Scrapping premiums — Special contribution — Transitional scheme — Principle that measures should not be retroactive — Principle of protection of legitimate expectations — Principle of proportionality)