Just a silly question, you being in SA, last time I was there, I noticed that all heavy goods vehicles seemed to used the same standardised rear LED lights.
Is that so, or was I simply in a meat eating stupor?
No, the rear lights are a mandatory standard on trailers over 1ton GVM, and have a defined diameter only. There is a series of manufacturers of lights, backing plates and mounting rubber boots for this standard. All are almost interchangeable, but the most common LED versions do tend to be capable of fitting the hole but have a flange and spots for 3 pop rivets to fasten them. Theft of the lights is the reason why, as the LED versions are 40 times the cost or more than the regular types.
There are a few varieties of the LED style as well, you must have only seen the one style in the harbour, which is the pop in type that is used by Portnet Operations, as it is a low cost lamp that is interchangeable with the regular incandescent lamp unit, fitting the same rubber mounting boot. I know of at least a dozen different styles, ranging from 3 red or yellow leds to ones that combine stop, tail and indicator in a single unit.
Of course on the majority of trailers they often do not work anyway, or have only a single led left lit, the rest are dead or flickering. The smaller transport companies, which are the owners of both the prime mover and the trailers, tend to have working lighting, as they are the ones that pay the fines. If it is a rental trailer then the lights, tyres and such often are in poor condition, along with things like legs, as the driver is not going to get fined for the trailer faults along the road, though if the trailer has new tyres and the prime mover has bald ones they might magically swap during the transport, or the spare tyres might do that.
Friend of mine had 14 flat tyres doing a delivery trip, but he had prepared before, having on the back of the truck both extra spare tyres, the built in crane and a compressor along with a big box of tyre patches and inner tubes, plus a fleet card for the truck stops. Rough road and a full load on the back. On the way he needed fuel, so stopped at the fuel depot only to be told that the bill is still unpaid, so no fuel. Luckily the load was jet fuel, and the load back was empty drums, which still have around 40l of fuel in them to compensate for water ingress. Crane a drum off, use their garden hose as a syphon and fill the drum from all the others, then lift up, drain with the hose till the water is gone and fill the diesel tank. Trucks run well on jet fuel........