Problem:

The Simple Distribution Method appears to give higher bending moments on edge girders than a simple static distribution?

Solution:

The Proportion Factor K_L makes no allowance for the position of the carriageway relative to the edge girder. Consequently a simple static distribution will often produce a smaller bending moment in the edge girder than the Simple Distribution method.
It is acceptable to use a simple statical distribution (see Clause 2.4) if the edge beam fails the Simple Distribution Method, but the internal girders should also be assessed using simple statics for consistency.