Should we flash the speeders?

MEATHMAN'S DIARY 

We’ve all had the same experience from time to time; at least those among us who are drivers. We’re motoring along minding our own business when we suddenly see him. Or maybe it’s a she?

He or she is usually strategically parked at some stop off or other where they can get a view of a straight stretch of road. They are the people who occupy the dreaded speed vans that can be seen around our roads from time to time.
I’ve never been inside a speed van but I imagine it as a dark place where the occupant (I imagine it is a man although there’s no earthly reason it shouldn’t be a woman) sits and stares at a monitor and takes down the numberplates of cars that are travelling above the speed limit.
The junction close to the old Kilcarn Bridge on the N3 near Navan is is one of those places where a speed van can be frequently seen; just sitting there like a tiger, coiled and ready to strike at any unsuspecting prey. 
When drivers see the van parked they invariably will start flashing their lights at oncoming traffic. It’s a warning. 
But should people be doing this? Is it right that they should flash their lights so that those who habitually drive at a high speed should be forewarned - and therefore allowed to evade punishment?
Those questions are all the more relavant especailly when we consider the number of people who die on our roads. Look at the figures. 
Last year 157 people were killed on Irish roads; the previous year the number was 186. It’s well recognised that speed is one of the main causes of those cold, truly horrifying statistics - yet people still drive at breakneck speeds. 
I been relieved at times to see lights of oncoming cars been flashed at me going into Navan on that road which has a speed limit of 80mph. I will automatically check my speed gauge to see if I am over the limit - and if I am I will slow down. I might be just a little over the limit but that’s hardly the point.  
Most people, it’s surely fair to assert, drive just over the speed limit especially on roads like the N3 if only for the simple reason that it's very difficult to stay under 80 mph. If you do the drivers behind you will start to get impatient. The harsh reality is that there are people out there who want to live on the edge.
We’ve all seen them in action; drivers who take outrageous risks such as overtaking at high speed at corners or on the brow of hill. Why should we warn these drivers? Why should we save them from the punishment they deserve? 
They are potential killers. The time has come, has it not, to keep those lights off when we see one of those speed vans parked on the side of the road?