Delivering major upgrades to one of Cape Town’s busiest roads

Project

Trunk Road 9/1 (Route N1) Widening Project  

Year

2013-2020

Location

South Africa

Client

Western Cape Government, Department of Transport and Public Works 

11
of additional median lane (upgrading 4 lane dual carriageway to 6 lanes)
5.5
of new concrete median barrier
6
of additional auxiliary lanes
4
interchange capacity upgrades
120,000
vehicles per day accommodated during construction

In May 2013, the Western Cape Government’s Department of Transport and Public Works appointed SMEC South Africa to provide the Road Network Management Branch with the full scope of professional services for the Trunk Road 9/1(Route N1) Widening – a freeway improvement project aimed at reducing traffic congestion and improving traffic safety over eight km of freeway between Jip de Jager Avenue and Durban Road in Cape Town.  

With approximately 120, 000 vehicles travelling along the route during the morning inbound and afternoon outbound peaks, accommodating the large volume of traffic on one of Cape Town’s busiest roads was a significant challenge. SMEC South Africa has played a vital role in the project for seven years, beginning with planning and then developing to concept and viability, design development, documentation and procurement, contract administration and construction supervision. The project was closed out in 2020.  

Our teams successfully delivered this mammoth project on time and within budget, with our client commending the outcome.

“SMEC South Africa successfully delivered this project within the constraints of the high traffic environment, while keeping the road user and the greater public well informed. This is a true example of the citizen-centric value that the Western Cape Provincial Government strives for.”

– Melanie Hofmeyr Chief Director, Road Design, Department of Transport and Public Works, Western Cape Government.

Challenges on a major freeway widening project 
The existing four lane basic dual carriageway needed to be widened to a six-lane cross-section by removing the grassed median island and building two inner lanes separated by a concrete median barrier. This variable height concrete barrier was designed specifically for the project using precast units to accommodate the level differences between the two carriageways. 

Additional road works included the upgrading of three interchanges at Jip De Jager Avenue, Old Oak Road and Durban Road and the construction of new auxiliary lanes between the interchanges on both inbound and outbound carriageways to improve weaving capacity.  

Structural work included the demolition and reconstruction of the Old Oak West Bridge over the freeway. The demolition of the existing overpass was particularly successful – the N1 was closed to traffic on the Friday evening and was reopened just 20 hours later on the Saturday afternoon – 28 hours ahead of schedule. Additional structural work included the construction of soil-nailed retaining walls and conventional reinforced concrete walls at the Jip de Jager Avenue interchange.  

Photo credit: South African National Roads Agency SOC Ltd (SANRAL).

In addition, the Wemmershoek Bulk Water Pipeline, a 60-year-old, 1200 mm spirally wound and embedded steel cylinder concrete pipe located in the freeway median, was replaced with a 1500 mm steel pipe outside the road reserve. Given its age, diameter, strategic importance and potentially catastrophic impact and excessive cost of repair, as well as sequential impacts following a failure, it was evident that the Wemmershoek Pipeline posed an extremely high risk for the project. This risk was well mitigated by the team through utilising a staged construction approach, relocating the pipe before any roadworks in the vicinity of the existing pipe location could commence. 

Ancillary works included a new street light system, new traffic signals at all interchanges and the removal and replacement of all overhead sign gantries, as well as the installation of a new Freeway Management System and sleeves for multiple fibre operators along the northern boundary. 

Delivering measurable outcomes 
The City of Cape Town’s regional macroscopic transport EMME Model, which models the effects of changes in the transport network and land use patterns in the Cape Metropolitan, was used to forecast traffic demand volumes after implementation of the project, as well as 20-year design horizon.   

These traffic demand volumes were used in VISSIM (a microscopic transportation modelling simulator) to calculate anticipated travel times and average speeds during the morning and afternoon peak periods. The results indicated a positive impact on the community, with a 75% improvement in average speed during the morning peak period in the peak traffic direction (a 14.4 minute saving in travel time in inbound direction during morning peak period), as well as a 65% improvement in average speed in the afternoon peak period in the peak traffic direction (a 8.9 minute saving in travel time in outbound direction during afternoon peak period) for the affected length of freeway after implementation of the project.   

The N1 is a national route in South Africa that runs from Cape Town through Bloemfontein, Johannesburg, Pretoria and Polokwane to Beit Bridge on the border with Zimbabwe. It forms the first section of the famed Cape to Cairo Road.

 A team of specialists collaborate for success 
The planning and design of the project involved specialists across multiple disciplines including traffic planners, freeway geometric designers, structural designers, and pavement structure designers, as well as the Bulk Water Department of the City of Cape Town and the planning and design teams of the FMS operator and fibre operators. In addition, the implementation required extensive liaison and cooperation with South African National Roads Agency Limited and the traffic departments of the Western Cape Government and the City of Cape Town. 

Despite the complexities involved in utilising a multi-disciplinary approach, collaborating across various workstreams and the extensive public-private cooperation required for implementation, SMEC South Africa successfully delivered this mammoth project on time and within budget.  

The strong performance and success of our team during the early stages of the project played a major role in the team securing another assignment with the same client, namely the Wingfield Project. This mega-freeway upgrade project is one of SMEC South Africa’s flagship projects and is currently in Preliminary Design Stage. 

Project

Trunk Road 9/1 (Route N1) Widening Project  

Year

2013-2020

Location

South Africa

Client

Western Cape Government, Department of Transport and Public Works 

11
of additional median lane (upgrading 4 lane dual carriageway to 6 lanes)
5.5
of new concrete median barrier
6
of additional auxiliary lanes
4
interchange capacity upgrades
120,000
vehicles per day accommodated during construction

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