Interesting road logic

Over the weekend I travelled north to the Copperbelt using the Mazhandu bus company who in terms of reliability, timeliness and safety tend to be the best in the country. At one point, just outside a town called Kapiri Mposhi (approx 3-4 hours from Lusaka), all heavy vehicles are forced to enter the weighbridge to be weighed. We queued up in haphazard fashion along with tens of other buses and trucks with each driver trying to manoeuvre their vehicle through the smallest gaps in order to get ahead in the queue. When it was our turn to pass through the weighbridge the officials found that the bus was overweight. In fear of being sent all the way back to Lusaka the solution was simple. The bus drove a few metres up the road, half the passengers were asked to depart and wait by the roadside, whilst the bus went through the same time consuming process again at the weighbridge. This time the bus passed the weight restrictions (possibly with something exchanging hands), we picked up the waiting passengers and continued to travel northwards. Now the point of the weighbridge is what exactly . . .?