The new system is a grid with odd numbers N-S and even numbers E-W - this clearly doesn't work with the N-S E4 and E6. They got given new numbers, but Sweden and Norway refused to sign them, having signed the old system E4 and E6 - the main routes through the two countries, that are very long. Given that E04 and E06 are routes for northern areas of Europe, they were naturally Norway and Sweden's anyway (ditto E8), so they simply redefined them to be the route of the old E4 and E6 through Norway and Sweden.
The E45 was to go along most of the E6 in Norway (the northern-most bit would have been E06), with the E47 covering the southern section to Oslo. The E4, and southern-most part of the E6 was to be E55.
The decision making process was much more complex than whether just retaining the numbers E4 and E6 or not. What was finally agreed, differs significantly from the first iteration
The original AGR agreement from 1975, in effect as of 1983, was initially signed by eight countries only. In that version, the E6 was replaced by E45 from Helsingborg to Vollan (Nordkjosbotn). The next version in 1985 showed E47 replacing E45 in Sweden and Norway, extended to Nordkapp, and introduced E06 Olderfjord-Kirkenes in Norway.
Sweden and Norway were not satisfied on the proposal, and withdrew their support from the AGR agreement in 1987. Instead, Sweden, Norway, and Finland created their own proposal which was accepted by the UNECE Inland Transport Committee in 1991. After agreeing on that amendment, those three countries signed the agreement.
The differences between the 1983 version and the 1991 one are the following (in Sweden, Norway and Finland):
- E10 Luleå-Kiruna-Å i Lofoten was introduced as a new W-E reference road (in the 1983 version, E20 was the lowest one).
- E75 Kemi-Tromsø was routed instead Kemi-Rovaniemi-Utsjoki. Tornio-Tromsø became E08.
- E18 was rerouted Newcastle-Kristiansand instead of Newcastle-Stavanger. E39 was moved from Germany (Giessen-Darmstadt) to Ålborg(Denmark)- Hirsthals(Denmark)- Kristiansand- Stavanger- Bergen- Ålesund- Trondheim.
- E20 Malmö-Ystad was routed to Malmö-Göteborg-Eskilstuna-Stockholm. E65 was extended from Ystad to Malmö. E37 Göteborg-Stockholm dropped.
- E45 was replaced by E06 which was extended to Trelleborg in the south and to Kirkenes in the north (thus retaining the number E6).
- E55 Tornio-Stockholm-Trelleborg was dropped and replaced by E06 Trelleborg-Helsingborg and E04 Helsingborg-Stockholm-Tornio-Kemi (thus retaining the number E4).
- E69 was moved from the central Europe (Warzaw-Wiener Neustadt) to Olderfjord-Nordkapp.
- E22 was extended from Sassnitz to Trelleborg-Malmö-Kalmar-Norrköping
- E140 Sundsvall-Trondheim was renumbered to E14, thus filling the gap between E12 and E16
- E136 Bergen-Oslo was renumbered to E16, thus extending the original E16 Londonderry-Edinburgh across North Sea to Norway.
- E135 Drammen-Haugesund was renumbered to E134 (as it is mainly W-E oriented).
- E137 Dombås-Ålesund was renumbered to E136 (W-E oriented).
- E160 Turku-Kuopio was renumbered to E63.