The Expert will be specific knowledgeable people at the Department of Transport, Arrive Alive Communications, the Road Traffic Management Corporation or others who might have the expertise to answer the question.
We often get asked this question, probably because we all know that a vehicle speeds up without any intervention from the driver when driving downhill. In fact, it is only by intervention on the part of the driver that a vehicle will maintain its speed whilst proceeding downhill.
Whilst it may not be regarded as being ethical by reasonable people for traffic authorities to trap vehicles proceeding downhill, the problem is that it is indeed 100% legal. In fact, most speed traps are set on downhill stretches of road.
The simple argument is that the speed limit remains the same whether you are proceeding uphill, downhill or on a flat surface and this wins hands down every time.
Since you are in the Cape Province, I thought I would also take the opportunity to inform you that the requirement for a fine to be issued (not necessarily received) within 30 days of the alleged offence does apply under the Criminal Procedures Act, however from 1 July, Cape Town will be subject to the provisions of the AARTO Act and under this Act, the period allowed for posting the infringement notice to you is extended to 40 days. Thereafter, if you do not collect the registered article from the post office within 10 days, it will be deemed to have been delivered after the 10 days have elapsed.