(39)Transitional measures should address not only the problem of certificates issued to boatmasters in accordance with Directive 96/50/EC, with Regulations for Rhine Navigation Personnel or with certain national legislation, but also the problem of certificates issued to other categories of deck crew members falling within the scope of this Directive. As far as possible, those measures should safeguard entitlements previously granted and should aim to give skilled crew members reasonable time in which to apply for a Union certificate of qualification. Those measures should therefore provide for an adequate period during which those certificates can continue to be used on the Union inland waterways for which they were valid before the end of the transposition period. Those measures should also ensure a system of transition to the new rules for all these certificates, in particular where journeys of local interest are concerned.