1. Contracting authorities may conclude framework agreements, provided that they apply the procedures provided for in this Directive.

A framework agreement means an agreement between one or more contracting authorities and one or more economic operators, the purpose of which is to establish the terms governing contracts to be awarded during a given period, in particular with regard to price and, where appropriate, the quantity envisaged.

The term of a framework agreement shall not exceed four years, save in exceptional cases duly justified, in particular by the subject of the framework agreement.

2. Contracts based on a framework agreement shall be awarded in accordance with the procedures laid down in this paragraph and in paragraphs 3 and 4.

Those procedures may be applied only between those contracting authorities clearly identified for this purpose in the call for competition or the invitation to confirm interest and those economic operators party to the framework agreement as concluded.

Contracts based on a framework agreement may under no circumstances entail substantial modifications to the terms laid down in that framework agreement, in particular in the case referred to in paragraph 3.

3. Where a framework agreement is concluded with a single economic operator, contracts based on that agreement shall be awarded within the limits of the terms laid down in the framework agreement.