High Quality Content by WIKIPEDIA articles! The N3 is a National Route in South Africa, connecting Johannesburg and Durban, respectively South Africa`s largest and third-largest cities. Johannesburg is the financial and commercial heartland of South Africa, while Durban is South Africa`s key port and one of the busiest ports in the Southern Hemisphere and is also a holiday destination. Durban is the port through which Johannesburg imports and exports most of its goods. As a result, the N3 is a very busy highway and has a high volume of traffic.