Major cities along its total length of 778 km (483 mi) include Oberhausen, Duisburg, Düsseldorf, Leverkusen, Cologne, Wiesbaden, Frankfurt, Würzburg, Nuremberg and Regensburg.

Consequently, large parts have three lanes (plus a hard shoulder) in each direction, including a 300 km (187.5 mi) section between Oberhausen and Aschaffenburg.

Until Oberhausen the highway runs on the right bank of the Lower Rhine past the cities Emmerich, Wesel and Dinslaken and reaches the Ruhrgebiet.

As the A 3 enters Bavaria, it intersects with the A 45, crossing the Main on the Mainbrücke Stockstadt and Aschaffenburg and the suburbs Goldbach and Hösbach.

Towards Passau, the highway runs parallel to the river past Straubing and Deggendorf (A 92 to Munich), traversing through the foothills of the Bavarian Forest.

Outside of Passau, the route turns south, passes through the Neuburg Forest and crosses the Inn, the border between Germany and Austria.

The first plans for the northern section between Emmerich and Oberhausen, the so-called "Holland line" (Reichsautobahnstrecke 92), date to the year 1936.

Despite difficulties in the route definition (industrial areas in Oberhausen and Dinslaken are crossed) was already in July 1939 with the construction to be started.

In 1929 the Provincial Association of the Prussian Rhine Province legally established the route between Cologne-Düsseldorf and in 1931 the construction started of a 2.5-kilometer section at Opladen.

In 1937, the northern continuation of the current motorway junction Oberhausen and the gap closure between Mettmann and Breitscheid followed.

The southern route allowed the direction Reichsautobahnen simultaneously from both Cologne in the south and Wiesbaden in the north.

The section between the interchange Köln-Mülheim and Siegburg 30 km in length was handed over on 17 December 1937 after about three years of construction time traffic.

The construction of the section south of the Wiesbadener cross with the Main Bridge between Raunheim and Eddersheim was started in 1938, but had to be discontinued in early 1943.

As a result, the signage had to be revised, the number of goals on the signposts was reduced, which was partly accompanied by a considerable loss of information.

At the same time, the junctions of this along the city limits Duisburg / Oberhausen running part of the motorway were renamed.

A fatal accident occurred on 23 October 2006, when a World War II aerial bomb exploded while milling a cement-lime mixture in the new hard shoulder.

In a highway renewal work in the summer of 2014, a 500 kg heavy bomb from the Second World War was found on 19 August between the Offenbacher Kreuz and the junction Obertshausen.

Two sections in the Frankfurt area are equipped with a special kind of facility to allow a temporary release of the emergency lanes during the rush hour.

These sections are monitored by cameras, so that the additional lane can be closed in critical situations, for example in case of a vehicle breakdown.

From the investment framework plan for the years 2011 to 2015 of the Federal Ministry of Transport, Building and Urban Development, the view was expressed that for the reconstruction of the AK Leverkusen and the expansion between the interchanges Leverkusen Center and Cologne-Mülheim, the planning should be promoted priority to start construction by 2015.

For the section between Mönchhof-triangle and the interchange airport (in the western part of the Frankfurter Kreuz) began in the spring of 2009, the planning approval process.

With the status urgent need is provided in the Federal Transport Infrastructure Plan 2003, the highway from Aschaffenburg on the Spessart and Main Franconia to the intersection Biebelried six-lane expand.

All sections not yet realized have been included in the investment framework plan for the years 2011 to 2015 of the Federal Ministry of Transport, Building and Urban Development as priority measures.

The 19 km long western subsection from the junction Aschaffenburg up to and including Kauppenbrücke was expanded in the years 2001 to 2011 on six lanes.

The 30 km long middle subsection, for which the Autobahndirektion Nordbayern in 2016 stated construction costs of 287 million euros, lies between the Kauppenbrücke and the Mainbrücke Bettingen.

[9] The approximately five-kilometer-long route between the Rohrbrunn junction and the Haseltalbrücke (including the expansion of the Spessart Süd refueling facility) has been under construction since 2016.

The plan approval decision has been in place since October 2008 for the 9.7-kilometre (6.0 mi) section to the Main; the expansion began in 2014 and was expected to be completed in 2017.

The 45 km-long (148,000 ft) eastern subsection, for which the Autobahndirektion Nordbayern 2016 construction costs of 574 million euros stated, lies between the Main Bridge Bettingen and the intersection Biebelried.

[10] In Fahrtrichtung Würzburg wurde im Steigungsbereich des Spessartaufstiegs ein zusätzlicher vierter Fahrstreifen errichtet.

The six-lane expansion of the route between the Biebelried interchange and the Fürth / Erlangen intersection is classified as an ongoing project in the new BVWP 2030 and is to be implemented via a public-private partnership.