When ascertaining the effective widths of class 1 and 2 composite girders, it is claimed that at ULS, Eurocode 4 procedures give highly conservative results. A new approach to the problem is proposed in which the strain limitation values are introduced after deriving a new formula (graphically presented) with the intention of replacing the existing one. It turns out that the new effective width is significantly larger. Such a result leads to some advantages in reinforcement distribution in the support areas of continuous girders. It might also lead to some savings in reinforcing and structural steel. This is demonstrated by an example. Another example shows a situation in which the rough application of Eurocode 4 may produce a design with a lack of reliability for some of the bridge superstructure elements. The results obtained may also be useful for situations where a structure with composite girders already in service has to be redesigned for increased loads.