So, scenario A:

    4 ton vehicle, 2 axles
    load per axle is 2 tonnes.
    2^4 is 16
    2 axles - so load is 32.
    Another vehicle the same - also loading 32
    Total: 64

    8 ton vehicle, 4 axles
    load per axle is 2 tonnes
    2^4 is 16
    4 axles - load load is 64
    Total: 64