This is important because if there is insufficient load transfer the loaded slab is likely to move downwards under load. Where this occurs when MHE is running over the joint/crack this will expose the arris which will then suffer impact loading from the MHE. Over time this impact loading will damage the arris and can lead to significant damage to the slab.
During design the slab should have dowels of sufficient strength at the joints to ensure load transfer will be maintained when trafficked by the heaviest MHE or when racking is fully loaded close to a joint.
Formed joints rely solely upon dowels placed during construction for load transfer whereas Induced joints such as sawn jointshowever provided that they do not open wide will have some aggregate interlock which provides load transfer. In the case of fabric reinforced slabs this aggregate interlock and is enhanced by dowel action from the steel in the bottom.