This project required significant upgrades to National Routes R21 and R24, which are key semi-urban to urban links between O.R. Tambo International Airport and Metropolitan areas. SMEC provided the full spectrum of Professional Engineering Services to deliver the project successfully within a tight timeline.

The upgrade aimed to increase the capacity of the R21 and R24 roads including related interchanges, crossroads and support facilities. This included widening of a 55 km four lane freeway to eight lanes (adding two additional lanes to each carriageway in the median); improving four interchanges; widening several bridges; improving drainage; providing lights in the median along the full length; and repairing and upgrading the cross-roads.


The project had a relatively tight timeline and works were carried out in three parallel contracts to ensure completion on time. A phased construction strategy was used which started with widening one carriageway and using this to accommodate two lanes of traffic in each direction with a dividing barrier. Subsequently the second carriageway was rehabilitated and widened and then used to accommodate four lanes of traffic in each direction while the original lanes of the first carriageway were rehabilitated. Bridge construction and other works fitted into this strategy.


The phasing of construction works, and constrained availability of construction materials were project challenges that were overcome with thorough planning and teamwork with the contractor and client.


Objectives of the project are to:

  • Improving the road network around a key transportation hub, within a tight timeframe.
  • The project significantly reduced congestion along the route and returned the R21 corridor to a roadway of choice.


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Talk to one of our specialists about our role on the R21 and R24 Upgrade Project.