M5 Road (Cape Town) - Design

Design

The elevated free ways embody some innovative design features and principles. For example: The elevated free ways had to be built without disrupting the daily flow of some 200 000 vehicles. The existing roads and bridges had already used up the available land into which to expand. The intersection is hemmed in by a canal, railway reserve, power transformer, and industrial buildings etc. Thus the possibility of overlaying the existing structures with a bypass had to be envisioned. It had to be a system that could fit into the existing interchange. Oval reinforced concrete pillars with "T" pieces atop, standing on foundations supported by concrete piles, could fit into the spaces between existing roads and bridges. These could in turn support post-tensioned concrete "U" beam spans, cast on the ground and lifted into place by crane. The road deck would be cast on top of the "U" beams. 5 Beams between each "T" topped pillar allowing for a double lane road deck. The beams resting on each side of the "T" piece support, are connected to each other and the deck by a concrete end which resists lateral-flexing of the deck between-beams.

The roadway on both elevated free ways narrows from a double lane to a single lane at the point where it connects with the existing N1 and the M5 motorways. At this point, the elevated free way presents the motorist with a down-hill slope to encourage acceleration. The elevated free way feeds into its own own lanes on both of these existing free ways allowing acceleration and preventing congestion.