1264, the Declaration on the Construction of Main International Traffic Arteries,[1][2] signed in Geneva on 16 September 1950, which defined the first E-road network.

[citation needed] The declaration was amended several times until 15 November 1975, when it was replaced by the European Agreement on Main International Traffic Arteries or "AGR",[3] which set up a route numbering system and improved standards for roads in the list.

However, since Sweden and Norway have integrated the E-roads into their national networks, signposted as E6 and E4 throughout, a decision was made to keep the pre-1992 numbers for the roads in those two countries.

These exceptions were granted because of the excessive expense connected with re-signing not only the long routes themselves, but also the associated road network in the area.

Further exceptions are: These irregularities exist just because it is hard to maintain good order when extending the network, and the UNECE want to avoid changing road numbers.

Because the Socialist People's Republic of Albania refused to participate in international treaties such as the AGR, it was conspicuously excluded from the route scheme, with E65 and E90 making noticeable detours to go around it.

In the 1990s, Albania opened up to the rest of Europe, but only ratified the AGR in August 2006, so its integration into the E-road network remains weak.

For example, the E45 in Sweden, added in 2006, has long parts with 6 m (20 ft) width or the E22 in eastern Europe forcing drivers to slow down to 30 km/h (20 mph) by taking the route through villages.

In Belgium, for example, motorway E-numbers have taken on the same kind of persistent cultural integration and significance as M-numbers in the UK, or Interstate numbers in the United States.