Mt Edgecombe Interchange
A decade after the project was launched in 2009, the upgrade of the iconic Mt Edgecombe Interchange in South Africa was officially completed in 2019.

Currently considered to be the largest interchange project in South Africa, the upgrade involved upgrading an existing diamond interchange layout to a free-flow, four-level configuration.

SMEC provided consulting engineering services throughout the decade-long project and overcame numerous design constraints and challenges to produce what has been described as “an outstanding example of technical expertise and quality which has contributed substantially to alleviating heavy traffic congestion and  contributing to the transportation efficiency  and the economy of the region” (judges’ comments, 2018 SAICE Durban awards).


A creative geometric solution to space constraints

Meeting the challenge of upgrading a heavily trafficked interchange connecting major collector-roads within significant space constraints required a successful combination of planning and innovative engineering design. These physical constraints included current and future developments, existing road reserve boundaries, traffic congestion, future traffic demands, the proximity of the Gateway Theatre of Shopping offramp from the M41 and preservation of existing stormwater attenuation areas.

Our specialists designed a creative geometric solution which took the form of a four-level, free-flow interchange with full-width directional ramps. This eliminated the need for controlled signalisation, thus ensuring the free flow of traffic in all directions whilst keeping the geographical footprint of the interchange as small as possible and largely within the constraints of the road reserve.

New or upgraded bridges
Longest bridge structure in South Africa
of ramps
Fulton Awards Winner
South African Institute of Civil Engineering Durban Branch Awards Technical Excellence Winner
Roads and Bridges Winner Consulting Engineers South Africa (CESA)
The R1,1 billion interchange, which is one of the largest projects undertaken by SANRAL in KwaZulu-Natal, is more than a masterpiece of award-winning architecture – it is a vital artery of the greater eThekwini metropolitan highway system and has greatly contributed to SMME development.”
———— South African National Roads Agency Limited (SANRAL), CEO, Skhumbuzo Macozoma

Engineering innovation sets new standards

While the project boasts many examples of engineering excellence, its most iconic features are the two upper-level ramp viaducts. One of these, Bridge B0215, has a deck length of 947 metres, which makes it the longest incrementally launched bridge in the Southern hemisphere, as well as the longest bridge structure to ever be built in South Africa. 

What sets the bridge apart, however, is that it was constructed in two decks, which were both incrementally launched from opposite sides and designed to meet in the centre. Ensuring that the two decks would meet up within dimension tolerances required innovative design, precision survey work, and sound construction management.

The final position of the decks was 7mm from the design position transversely, and 0mm from the design level vertically. Given their size and the fact these decks were launched from opposite ends, this accurate final position is a testimony to the intricate workmanship and world class engineering capabilities of SMEC’s specialists in South Africa. 

A vital artery in both transportation and economic systems

The Mt Edgecombe Interchange is on the N3 at Umhlanga, KwaZulu-Natal, one of the fastest developing areas of South Africa. This consideration played a major role in the conceptual design to ensure that the interchange would aesthetically complement its fast-paced modern surroundings; stand the test of time in terms of life-span; and have capacity for the ever-increasing traffic demands.

In addition to its status as a civil engineering work of art, the upgraded interchange has changed the landscape in more ways than one. It is contributing significantly to easing traffic congestion, supporting safer road travel, and enabling economic growth. 


Talk to one of our specialists about our role on Mt Edgecombe Interchange.