For those still trying to work out how a lorry driver and a weighbridge operator can fool the system, here's one very simple method:
The lory driver (who weights 75kg) takes his vehicle onto the weighbridge, gets out and steps off the weighbridge. The weighbridge operator presses the button which electronically records the weight of the lorry. When the vehicle is on its way out, the driver again takes it onto the weighbridge but remains in the cab. The weighbridge operator presses the button to record the exit weight. The difference between the two figures ought to show how much waste has been tipped but,because of the driver's actions, it will be 75kg short. (If it's a really old-fashioned weighbridge, where the operator simply writes the figures down instead of them being recorded electronically, it's even easier to fiddle the figures as he simply needs to adjust the figures manually).