Bundesstraße
One distinguishing characteristic between German "Bundesstraßen" and "Autobahnen" is that there usually is a general 100 km/h (62 mph) speed limit on federal highways out of built-up areas, as opposed to the merely advisory speed limit ("Richtgeschwindigkeit") of 130 km/h (83 mph) in unmarked sections of the autobahns. However, a number of "Bundesstraßen" have been extended as expressways (dual carriageways) (colloquially called "Yellow Autobahns"). Many of these have speed limits of usually 100–120 km/h, others have only an advisory speed limit like autobahns. Most sections of the federal highways are only single carriageway with one lane for each direction and no hard shoulder pull-out area.
Dual carriageway
"Autobahnähnliche Straßen" mostly are colloquially referred to as "gelbe Autobahn" (yellow motorway) because they have the same technical standard as the "Autobahn" but have black on yellow signs instead of the white on blue signs used on the "Autobahn" motorway network. These are generally high-speed arterial roads in larger cities or important roads within a federal state that do not connect to major cities, so that they do not fall under the federal budget for the "Autobahn" network. The federal road Bundesstraße 27 is an example where about half of its length is upgraded to a high speed motorway standard. On the basis of their structure these roads have, comparable to the German "autobahn", the legal foundation that no default speed limit exists (design speed 130 km/h), although the standard advisory speed limit () still exists. Nevertheless expressways are often given speed limit signs.
At the moment some (blue) motorways have been taken out of the "Autobahn" network programme but still have the blue signs; and on the other hand some former non-"Autobahn" (yellow) motorways have been added to "Autobahn" budgeting but the signs have not been changed either. Motorways that are neither in the "autobahn" network nor in the "Bundesstraße" network are given black on white signs, following the same sign code as high-speed dual carriageways—this is mostly seen on urban trunk roads.