White heart on red background signs on lamp posts in Cape town

I have tried to find a link to the road signs in several places in Cape Town, but have not yet been able to find the meaning.

They occur on the road from Kirstenbosch to Cape Town at about

33°58'28.6"S 18°26'51.3"E

and on the road from Table View to Cape Town near Rietvlei at about

33°50'21.3"S 18°29'09.8"E

There are a lot of hits to searches for road signs with hearts, but nothing that seems to relate to this particular road sign.

It does not seem to relate to http://secretloveproject.co.za/.

The best match that I can find is The Heart and Stroke Foundation of South Africa http://www.heartfoundation.co.za/

Why is it that these signs are popping all over the place and I cannot find what they signify or symbolise?