Due to the increase of the international motor vehicle traffic the idea to facilitate the operation of the system changed in spite of the satisfactory functioning of the Green Card system. The members of the Green Card system raised the idea of concluding supplementary agreements which are aimed at the elimination of producing and controlling the Green Card as a documentary evidence of the insurance cover.

In the beginning the member countries concluded bilateral supplementary agreements. These accepted either mutually or unilaterally the registration number and the country designation as an evidence of the insurance cover. This depending on which of the parties was willing to provide a guarantee for the vehicles registered in his own country when crossing the other country’s border.

In December 1973 these agreements were first substituted by a so-called Supplementary Agreement of several countries, then on 15th March 1991 it was replaced by the Multilateral Guarantee Agreement.

This agreement was extended to Green Card Bureaux of all those countries which previously signed bilateral agreements accepting the registration number as the evidence of the insurance cover.