(27 Aug 2015, 8:26 pm)G-CPTN wrote We used to reckon:- "20 inches one bum, 20 bums one ton." - but that was a rule of thumb that has been exceeded by people being heavier these days (at least heavier than 8 stone, though it included women and children).
I notice that the chassis is rated at 18 tonnes (also the maximum for two-axle double deckers - though I see that Volvo quote 18 tonnes for the B9TL ?) but I haven't found any unladen weights yet.
If you average passengers at 12 stone (though many might be heavier so you might have to allow for 15 stone average to remain within the GVM) then a full load (without luggage) should be within 10 tonne - that only leaves 8 tonne for unladen weight.
I believe that B9TLs are about 11 or 12 tonnes unladen (with extra bodywork of course).
I wonder if any bus has ever been caught being overweight?
I'm going to guess the MPDs for a start.