For those of you who wish to peruse the Traffic Act
http://www.info.gov.za/gazette/acts/1996/a93-96.htm
And the new traffic regulations
http://www.autoworld.co.za/NewsArticle.aspx?Article=7176
The only referance to headlights i could find is from the new traffic regulations:
Driving between sunset and sunrise without lights
Not using dipped beam with oncoming traffic
"sorry , officer, i was only dipping my headlights per the new regulations"
Wiki gives a nice explanation :
Headlight flashing is commonly used to warn other drivers of dangers on the road, such as crashed cars or police speed traps
http://en.wikipedia.org/wiki/Headlight_flashing
Speed traps are dangers, i have seen many drivers adhering to the speed limit, suddenly slam on brakes at the sight of a hidden speed trap, even though they are not over the speed limit, now if you are sitting behind one of these morons and towing a trailer, caravan or boat, instinctively you do the same, this can very easily result in you trailer jacknifing, and could cause an accident.
You cannot be found guilty of Defeating Or Obstructing The Ends Of Justice
http://www.legalcity.net/Index.cfm?fuseaction=RIGHTS.article&ArticleID=1418800
You can be found guilty for Obstructing The Police
To warn a speeding motorist of a speed trap also constitutes obstruction.
However Before a person can be found guilty of obstructing the police, it must be shown that the police were lawfully exercising their powers or duties.
http://www.legalcity.net/Index.cfm?fuseaction=RIGHTS.article&ArticleID=8094126
Does hiding in the bushes constitute lawfull behaviour on the part of the police, considering it is not visible policing ?
Then of course they have to prove you were actually trying to warn the other motorist.
IMHO, the biggest beef the police seem to have here is not about the actual criminals, but the loss of revenue that speed traps and roadblocks generate, because in essence, thats their sole purpose, to generate revenue.