Permanent and mandatory traffic signs

Question

Please can you tell me whether the yellow and black speed signs is mandatory? I.e. if there are roadworks on the freeway, and the speed limit is normally 120 km/h, there is a 60 km yellow sign, can you get a speeding fine for not doing 60 km?

Answer

White background signs are 'permanent' signs, meaning they generally apply all the time.

Yellow background signs are temporary, and they overrule any white background version nearby, because the temporay situation (e.g. roadworks) usually requires a different instruction due to more hazardous conditions.

Also view: http://roadsafety.co.za/2009/06/04/be-attentive-to-temporary-speed-signs/