The beltway was constructed in a clockwise fashion beginning at Leverkusen. In 1936 the section between Leverkusen and Cologne-Mülheim was built as a component of the Autobahn Oberhausen-Wiesbaden and in 1937 the section to Siegburg was finished. Thus today's Ostring was drivable at that time. In 1941, the Rodenkirchener Autobahnbrücke was completed and the connection between the A 3 and the Autobahn to Bonn was established. From 1957 to 1960 the Autobahn Cologne-Aachen was finished and the section from Kreuz Köln-Süd to the later Kreuz Köln-West was put into service in 1958. Construction of a second Autobahn-bridge across the Rhine in the north of Cologne began in 1961. At its completion, the beltway could be used along its entire length. In 1971, the A 1 was extended to the south beyond the Köln-West interchange and in 1974 the A 4 was connected to the A 3 from the east at the Köln-Ost interchange. Since then, the section between interchanges Kreuz Köln-Ost and Dreieck Heumar consists of two Autobahns, the A 3 and the A 4.
Current state
Traffic volume on the Cologne Beltway has been increasing continuously since the 1950s. Almost all sections, with the exception of a short stretch on the A1 between Kreuz Köln-West and 1km north of Köln-Lövenich, have since been expanded to three lanes in each direction, but since more than 180,000 cars use at least part of the Autobahnring every day, traffic jams are a frequent occurrence. The section between the interchanges Kreuz Köln-Ost and Dreieck Heumar was expanded to four lanes in each direction in 2005, a first for North Rhine-Westphalia. In 2008 the section with four lanes in each direction has been extended to the interchange Köln-Dellbrück. Currently widening work is going on between Köln-Dellbrück and Köln-Mülheim. It was scheduled to be complete in autumn 2012. The A1 has mostly a speed limit of 100 km/h. It has recently been raised to 120 km/h northbound between Köln-Lövenich and Köln-Bocklemünd as well as between Kreuz Köln-Nord and Köln-Niehl. On the A4 the speed limit is 120 km/h. On the A3 there is a variable speed limit up to a maximum of 120 km/h. In preparation for the 2006 FIFA World Cup the A 3 was outfitted with a traffic management system which is able to route traffic around congestion and construction sites.
"Second Beltway"
In the 1970s, a second beltway around Cologne was considered, incorporating existing Autobahns, instead of expanding the first one to more lanes. An expansion of the old beltway was considered as too expensive because of the large number of bridges. It was planned to incorporate some of Cologne's other Autobahns into this second Autobahnring. These plans were however never implemented.
