Improved analyses of remaining fatigue life – performance test of damage equivalent factors λ. This contribution is dealing with the concept of damage equivalent factors (Formula presented.) for assessment of the remaining fatigue service life of steel railway bridges, as it is also used in the relevant national guidelines for existing structures. However, what is considered here is not the suitability of country-specific traffic mixes, but only the effects of the implicit calculation assumptions of this concept on the results of the fatigue damage – and subsequently the remaining fatigue service life of existing bridges. On the one hand, it is analysed whether these (Formula presented.) -factors – which are always based on the shape of the influence line for the bending effect of a single-span beam at midspan – also produce accurate results for other practical shapes of influence lines (e. g. for components of open bridge decks, or members of truss main girders). On the other hand, it is also shown, that the actual fatigue strength (Formula presented.) of the existing structure, which is not included in the (Formula presented.) -factors and is usually higher than implicitly assumed, can lead to conservative results and offers potential for an improved alternative assessment of the remaining service life. © 2024 Ernst & Sohn GmbH.