Autobahns of Austria
Unlike German autobahns, on Austrian autobahns a general speed limit of 130 km/h (81 mph) is set, although as of August 25, 2018, the FPÖ government has been going on a trial for a possible speed limit increase to 140 km/h (87 mph) on the Autobahn 1 freeway. They may only be used by powered vehicles that are designed to achieve at least . While on the motorway voluntary stops, U-turns and backward driving are prohibited.
Bundesautobahn 4
The A 4 starts north-west of Aachen, where the Dutch A76 enters Germany. Initially it is 2 lanes each way with no speed limit. From Kreuz Aachen to Düren and from Kerpen to Refrath (between Refrath and Köln-Merheim westbound the hard shoulder is the 3rd lane and only open at peak times) it has 3 lanes each way. Between Kreuz Köln-West and Kreuz Heumar it forms the southern part of the Cologne Beltway (Kölner Autobahnring). The whole rest of the section between Kreuz Aachen and Kreuz Köln-West has a variable speed limit. Between Merzenich and Elsdorf, there is a speed limit of 130 km/h, that has been imposed in 2017, due to an increase of accidents. Between Kreuz Köln-West and Kreuz Heumar the speed limit is 120 km/h. From Kreuz Köln-Ost to Refrath there is a maximum limit of 100 km/h. The westbound section between Köln-Merheim and Kreuz Köln-Ost is restricted to 80 km/h. The section between Refrath and the current terminus at Krombach has no speed limit. Only between Untereschbach and Refrath westbound there is a 100 km/h speed limit from 6 - 10 am on weekdays. It is mostly 2 lanes each way, but between Untereschbach and Wiehl there are several additional climbing lanes in both directions.