Amsterdam to Rotterdam

The A4 begins in the province of North Holland in the southeastern part of the city of Amsterdam at an interchange on the A10 ring road called Knooppunt De Nieuwe Meer. At this interchange, the E19 continues from the eastern segment of the A10 onto the A4, and the E22 begins northwards along the A10. Even though the A4 starts at this interchange, the A4 has priority from the eastern direction toward the interchange, as entering onto the A4 from the east does not require a turn (in contrast to staying on the A10, which requires a turn to the right).

From the north, staying on the A10 and entering the A4 both require a turn. From the Knooppunt De Nieuwe Meer interchange, the road travels to the southeast, concurrent with a rail line that runs between both directions of the motorway. After 4 kilometres (2.5 mi), the road intersects A9 at the Badhoevedorp partial cloverleaf interchange. After leaving this interchange, the rails travel southwards underground towards Amsterdam Airport Schiphol.

Heijningen to the Belgian border

The final segment of the A4 with the A29 starts in the province of North Brabant near Heijningen at the Hellegatsplein interchange, crossing the estuaries Hollands Diep (to the east), Haringvliet, and the Volkerak (to the west). Shortly after, the A4 enters the Sabina trumpet interchange (named after a nearby fort) with the A59. The A29 and the A59 both enter this interchange from the north, and the A29 ends here. The A4 continues to the south, while the A59 branches off to the east.

Crossing the Dintel and passing by Dinteloord, the A4 makes a large curve to the west and subsequently continues to the south, forming a tangent around Steenbergen. In the southern part of the curve, the A4 travels along Fort Henricus, a now-demolished fort with only the shape of the land intact. Here, the road also tunnels under the Steenbergse Haven using the third Steenbergen aan Zee aqueduct.

The A4 continues southbound and passes Bergen op Zoom to the east, with a few exits serving this city. Between exits 27 and 28, the A58 runs concurrent with the E312, which joins A4 to the south. All three roads travel concurrently southbound, and at the Markiezaat trumpet interchange, the A58 and the E312 both leave the A4 and travel to the west, entering the province of Zeeland. The A4, however, continues to the south until reaching the Belgian border near Zandvliet. A few meters before crossing the border, the northbound entrance and southbound exit ramps start on Dutch soil; the rest of this exit is within Belgium and is part of the Belgian A12.

20th century

Work started on A4 in the 1930s, and followed high construction standards for the time. By the late 1930s, various sections were in service. One of these roads went between Amsterdam and Sassenheim, and while part of the historical A4, it is not on the current route.

In 1938, ground was broken for Rijksweg 4A, which went between Burgerveen and Leidschendam. This road would later be renumbered to Rijksweg 4, and it now forms a section of A4. Groundwork began in 1939 near Leidschendam, but was cancelled in 1942 due to World War II. Construction of the Ypenburg interchange also started that same year.

In 1957, the A4 opened between the Ypenburg and Leidschendam interchanges, the latter now known as Prins Clausplein, with 2 lanes in both directions. Construction from the latter interchange further north to Hoogmade was done in 1958. In 1960 and 1961, the section between the Burgerveen and Hoogmade interchanges opened, including an aqueduct underneath the Ringvaart canal.

One lane of Rijksweg 4 between Klaaswaal and the Hellegatsplein interchange opened in 1964, and in 1965, another lane was added. This section is currently designated as the A29. In 1966, another standalone section of the A4 was opened with 3 lanes in each direction, between Amsterdam (where the Badhoevedorp interchange is now located) and Hoofddorp, leaving a gap between Hoofddorp and the Burgerveen interchange. The Badhoevedorp interchange, which is between Amsterdam and Hoofddorp, was opened a year later in 1967, which was the first cloverleaf interchange with collector/distributor lanes in the Netherlands. In 1972, this segment of the A4 was lengthened northward to connect to the De Nieuwe Meer interchange. Another unconnected section of the A4 was constructed at the Kethelplein en Pernis interchange in 1967 in western Rotterdam. This included the construction of the Beneluxtunnel under the Nieuwe Maas, which was a tolled tunnel at construction but was converted to free in 1980. In 1972, this section was extended southward to the Benelux interchange.

In 1971, the sections of Rijksweg 4 designated as A29 were extended from the Hellegatsplein interchange to Dinteloord. It was first administratively and publicly known as Rijksweg 19, but in 1976, it was renumbered to Rijksweg 4 and designated as A29. Another section of Rijksweg 4 concurrent with A58 was opened around Bergen op Zoom between 1973 and 1976. In 1985, the Leidschendam interchange was renamed and redesigned to a 4-level stack interchange Prins Clausplein. The segment between Badhoevedorp and Hoofddorp was widened to 2x4 lanes in 1988, and ten years later in 1998, the tubes in the Schipholtunnel were renewed.

In 1993, the section around Bergen op Zoom was extended southwards from the Markiezaat interchange (where concurrency with A58 stopped) to the Belgian border near Zandvliet, where it connected to the Belgian A12. In 1999, the section between The Hague-Zuid and Delft-Zuid opened for traffic after the section between the Ypenburg interchange and The Hague-Zuid was opened with 3 lanes in each direction in 1998.

21st century

In 1998, the A4 between Zoeterwoude and Leidschendam was widened to 2x3 lanes, and in 1999, the part between Leidschendam and the Prins Clausplein interchange was widened to 2x5 lanes. In 2003, a new set of express lanes was added to both directions between Hoofddorp and the Burgerveen interchange, giving this segment a total of 2x5 lanes. Formerly restricted to rush hours, these express lanes were permanently opened on 2 April 2013.^[4] In 2006, the segment between Hoogmade and Roelafarendsveen was widened to 2x3 lanes.

In 1997, construction had started on the second Beneluxtunnel in Rotterdam. On 11 May 2002, the project was completed with 4x2 lanes and a reversible lane, allowing for 5 available lanes in the peak direction. Between the De Nieuwe Meer and Badhoevedorp interchanges in southwestern Amsterdam, express lanes were added in 2011 to relieve the 2x3 lanes on this segment of the A4 during rush hours, which saw use by 180,000 vehicles every day. Construction for the express lanes was started in the summer of 2010. The same year, construction also started on new lanes between Hoofddorp and Hoofddorp-Zuid for the construction of the realigned N201, commissioned by the province of North Holland. These parallel lanes are between the Den Ruygen Hoek rest area and Schiphol exit. Work was completed on 15 December 2013.

Entering the Burgerveen interchange from the north, the A4 has 2x5 lanes, which is reduced to 2x2 after leaving the interchange. Even though a lot of traffic is headed to the A44 at this interchange, this was still an important bottleneck, with some 100,000 vehicles every day in the Ringvaart aqueduct that also lacked emergency lanes. Further south, the bridge over the Oude Rijn river was another bottleneck with only 2x2 lanes. After this segment, 2x3 lanes were once again available. The A4 towards Amsterdam was widened to three lanes between Hoogmade and Roelfarendsveen in 2005, with a lane added to the other direction the following year. The low bridge over the Oude Rijn was replaced by the Limes aqueduct, making the A4 deeper than 1,400 metres (4,600 ft). A second Ringvaart aqueduct was also constructed near Roelfarendsveen, which was formally opened on 31 July 2010, after which the existing aqueduct from 1961 was renovated. On 24 November 2010, the 2x3 lanes were formally opened by minister Melanie Schultz,^[5] significantly reducing traffic congestion as a result. The opening of the Limes aqueduct was in two phases. The first aqueduct was opened in 2012 next to the existing A4, almost immediately with 2x3 narrowed lanes, after which the old A4 was destroyed and the construction of the second aqueduct was started. On 25 October 2014, the second aqueduct opened. The aqueduct has space for 2x5 lanes, plus emergency lanes. The aqueduct was completely widened on 1 December 2014, when the aqueduct toward The Hague gained three normal-width lanes.

Delft-Kethelplein missing link

A4 south of Delft on 20 December 2015. Right (northbound) lanes are already opened for traffic; left (southbound) lanes are still closed and are expected to be opened later in the day.

Until 2015, the A4 southwest of Delft had its southern terminus of the section start in Amsterdam, with another section starting at the Kethelplein interchange in Schiedam and running southwards. The missing segment caused huge congestion on the adjacent parallel A13, which was the only motorway connecting The Hague and Rotterdam. There have been plans for creating this missing link in the past, but the government diverted finances to other projects twice. In 2006, it was estimated that this 7-kilometre-long (4.3 mi) missing section would cost €700 million to build, and in 2009, the Dutch government decided that this section would be constructed. On 2 September 2010, minister Camiel Eurlings made a record of the decision for this road segment, and on 6 July 2011, all appeals against the decision were dismissed. In autumn 2011, construction began. The missing link was completed in late 2015 and was opened on 18 December 2015 (northbound) and 20 December 2015 (southbound).^[6][7]

Benelux-Klaaswaal missing link

At this point in time, there is no motorway between interchange Benelux and the A29 near Klaaswaal. However, an extension of the A4 southwards is possible without changing the layout of the Benelux interchange. This missing section was already approved by the government in 1961, as part of the then-called Road 19, and space was reserved by the government in 2005. By constructing this missing link, the A4 would be one continuously running road from the Kethelplein interchange, west of the city of Rotterdam, to the Belgian border. It would also relieve the A15 and A29 from traffic jams, since they currently serve as a link between the two sections of the A4.

Supporters of the planned 12-kilometer-long motorway state that cities like Hoogvliet, Spijkenisse, Barendrecht and Rotterdam would be significantly less congested, and that overall traffic flow would be restored. Opponents, among which are environmentalists, state that the construction of the missing link would only result in more traffic and thus more congestion, leading to negative environmental effects. Since the A15 and the A29 are currently being widened, this section of the A4 seems more and more unlikely to be built.

The motorway section between Klaaswaal and the Sabina interchange near Dinteloord is currently known and designated as the A29, but the intention is to include it in the A4 motorway and designate it as such in the future. When the missing link between interchange Benelux and Klaaswaal is completed, this section will be renumbered to the A4, in order to create a continuously numbered motorway between the Kethelplein interchange and the Belgian border. For now, however, this section of road is still being numbered as the A29 to avoid confusion.