Faulty Brakes on Caravans

12 months ago my wife and I purchased the Peak Hill Caravan Park. As ours is a small park we do not have all the roadways sealed and this has enabled us to observe caravans with faulty electric brakes. We estimate that 5% of the caravans that we guide into their site have only one wheel with a break operating, causing this wheel to lock up and skid on the gravel surface. The big problem is that when we discuss this with the driver they are completely unaware of the situation and in most cases say that they have “adjusted the breaks up a bit” so the van still slows them under normal breaking. This action only makes the situation even more dangerous as now under heavy breaking the van will push the rear of the car sideways causing it to either run off the road or out into the oncoming traffic.
I have attempted to contact different people and organisations regarding this situation without any reply. I believe that with the ever increasing number of caravan that are now travelling our highways at or even above the 110km speed limit that there has probably already been some accidents caused by this situation.
There must be a monitoring device available that will alert the driver when this fault has occurred, just like there is available on some cars an indication when tail or brake lights have failed. Does anyone know of such a device or how I can get this issue raised at an organisation that both cares and has the ability to act?
Leighton