The N3 begins in the Durban Central Business District at Pine Street and Commercial Road as a dual-carriageway freeway and heads west, passing through Berea and Mayville before intersecting with the N2 highway (Durban Outer Ring Road) at the EB Cloete Interchange.

It then exits the city of Durban and heads through the satellite town of Westville before passing to the south of Pinetown.

From Cato Ridge, the route passes Camperdown before turning towards the northwest and heading towards Pietermaritzburg, the provincial capital.

After bypassing Pietermaritzburg Central to the east and north, the N3 heads up a steep incline, whereby the road ascends from an altitude of 600m to an altitude of 1,100m in a northerly direction, known as Town Hill before passing near Hilton and Howick; a road to the Southern Drakensberg (the R617) leaves the N3 at Howick.

Just past Estcourt, access to the Central and Northern Drakensberg via the R74 is provided, before the N3 heads in the direction of Ladysmith (crossing the Tugela River).

The N3 from Cedara (in-between Hilton and Howick) to Heidelberg in Gauteng is managed by a private concessionaire, the N3 Toll Concession.

Just before reaching Heidelberg, the N3 has its last tollgate (De Hoek Toll Plaza); this also marks the point where the N3 crosses into Gauteng.

The N3/N12 concurrency proceeds northwards from the Elands Interchange and passes in-between the cities of Johannesburg and Germiston (Capital of Ekurhuleni).

[7] Following the opening of the motorway section in December 2001 between Heidelberg and Villiers, the N3 now has at least two lanes in each direction for its entire length between Johannesburg and Durban.

From Warden to Keeversfontein (Tugela Toll Plaza; Ladysmith) the road is no longer motorway but retains two lanes in each direction.

The N3 Toll Concession (N3TC) entered into a 30-year toll road concession contract with SANRAL on 2 November 1999 to manage the section of the N3 national route from Cedara (in-between Hilton and Howick) in KwaZulu-Natal to the R23 interchange on the southern side of Heidelberg in Gauteng, approximately 418 kilometres in length.

This has caused a huge outcry among residents of Harrismith and Van Reenen, who rely on passing traffic to sustain businesses such as restaurants, petrol stations, and holiday rest places.

There are toll plazas at Mariannhill (Pinetown), Mooi River, Tugela (Ladysmith), Wilge (Villiers) and De Hoek (Heidelberg).

[14] A sixth toll plaza would have been constructed south of Warden when the De Beer's bypass (mentioned above) would have been built.