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1. (a) The Contracting Parties to this Convention accept the system of road signs, signals and symbols and road markings described herein and undertake to adopt it as soon as possible. To this end, (i) Where this Convention prescribes a sign, symbol or marking for signifying a certain rule or conveying certain information to road-users, the Contracting Parties undertake, subject to the time-limits specified in paragraphs 2 and 3 of this Article, not to use any other sign, symbol or marking for signifying that rule or conveying that information;
(ii) Where this Convention does not prescribe a sign, symbol or marking for signifying a certain rule or conveying certain information to road-users, it shall be open to the Contracting Parties to use for these purposes any sign, symbol or marking they wish, provided that such sign, symbol or marking is not assigned a different meaning in this Convention and provided that it conforms to the system prescribed by this Convention.
(i) Where this Convention prescribes a sign, symbol or marking for signifying a certain rule or conveying certain information to road-users, the Contracting Parties undertake, subject to the time-limits specified in paragraphs 2 and 3 of this Article, not to use any other sign, symbol or marking for signifying that rule or conveying that information;
(ii) Where this Convention does not prescribe a sign, symbol or marking for signifying a certain rule or conveying certain information to road-users, it shall be open to the Contracting Parties to use for these purposes any sign, symbol or marking they wish, provided that such sign, symbol or marking is not assigned a different meaning in this Convention and provided that it conforms to the system prescribed by this Convention.
(b) With a view to improving traffic control techniques, and having regard to the usefulness of carrying out experiments before proposing amendments to this Convention, it shall be open to Contracting Parties to derogate from the provisions of this Convention, for experimental purposes and temporarily, on certain sections of road.
2. Contracting Parties undertake to replace or supplement, not later than four years from the date of entry into force of this Convention in their territories, any sign, symbol, installation or marking which, although it has the characteristics of a sign, symbol, installation or marking belonging to the system prescribed by this Convention, is used with a different meaning from that assigned to it in this Convention.
3. Contracting Parties undertake to replace, within fifteen years from the date of entry into force of this Convention in their territories, any sign, symbol, installation or marking which does not conform to the system prescribed in this Convention. During this period, in order to familiarize road-users with the system prescribed in this Convention, previous signs and symbols may be retained beside those prescribed in this Convention.
4. Nothing in this Convention may be construed as requiring the Contracting Parties to adopt all the types of sign and marking prescribed in this Convention. On the contrary, Contracting Parties shall limit the number of types of sign or marking they adopt to what is strictly necessary.